Epidemiology in Nursing-16-91

NSS 305 EPIDEMIOLOGY IN NURSING
3.0MAIN CONTENT
3.1 Definition of Epidemiology
Epidemiology is the study of the distribution and determinants of health-

related states or events in specified populations and the application of
this study to the control of health problems (J.M. Last, 1988).
Epidemiology was coined from a Greek word meaning the science of
people. Historically, the impact of epidemiology on the health of the
nation has been long-standing and far-reaching. Its origins can loosely
be traced to the time of Hippocrates (460-377 BC) who, as a physician,
attempted to investigate the occurrence of disease on a rational basis. In
Britain, its formative roots can be traced back to isolated studies of
specific diseases in the early 19th century. These investigations
culminated in the celebrated study by John Snow (referred to as the
Father of Epidemiology) who, around the 1850s, observed patterns of
incidence of a cholera outbreak in central London. As a result of his
recording of the incidence of cholera and mortality in the area, Snow
was able to isolate the cause of the cholera epidemic and attribute it to a
communal water-pump in Broad Street, Soho. After removing the pump
handle, Snow observed that new cases of cholera in the area ceased and
the epidemic declined.
Although dismissed by most scientists of the time, this finding and

others related to disease and the environment had a profound effect on
the formation of the public health movement and the early Public Health
Acts of 1848 and 1875.
Originally, the term epidemiology meant the study of epidemics, but the
techniques have long been improved upon. It is an applied discipline and
a basic science of preventive and social medicine (not theoretically) and
methods are essentially observational. Thus the modern definition of
epidemiology accommodates three important elements namely:
inclusion of al diseases, populations, and ecological approach. Please
note the three components (3Ds) common to the definition of
epidemiology: disease frequency, distribution and determinants. In
addition, the following terms are used to describe the extent of the
occurrence of disease: endemic, epidemic and pandemic.
The major questions that are usually asked in epidemiology are: who are
the group of person (s) affected by the disease, where has the incidence
occurred? and when (time) did it occur?
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SELF ASSESSMENT EXERCISE 1
Highlight the three important component of epidemiology
1.________________________________________________________
2.________________________________________________________
3.________________________________________________________
3.2Significance of Epidemiology
The following reasons have been adduced for studying these three ‘ds”:
disease frequency, distribution and determinants of diseases in
human population:
• For planning and evaluation of health care

• For identification of the determinants of diseases
• For evaluation of method of controlling disease
• For observation of the natural history of a disease – making up of
diagnosis and prognosis
• For classification of a disease.
Using at least 3 out of the reasons in 3.2 above, discuss among

yourselves how these are applied in your environment.
3.3 Uses of Epidemiology
Please recall from the activity above that the study of disease
distribution and causation is central to epidemiology. The broad
grouping of the uses occurs is in the following areas namely:
1. Understanding the causation of the disease and the development of

hypothesis and their testing
2. Understanding of geographical or local patterns of the diseases.
3. Administration (i.e.) the planning of health activities and direction of
programme to relevant sub-group identified to be at risk
However, epidemiology is used for the following:
• To analyze the respective role of agent, host and the environment in

the development and the natural history of disease.
• To analyze the occurrence and distribution of disease according to
characteristics such as age, sex, race, occupation and heredity.
• To study, outline and define problems of health and disease by the
analysis of incidence, prevalence and mortality.
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• To help the to complete the clinical features and natural history of

diseases by group analysis
• To estimate an individual’s risk of developing a disease and his
survival chances.
• To search for factors related to health and disease through the
observation of group custom and habits.
• For planning and allocation of resources
• To evaluate the need for and the effectiveness of health service
through field studies.
4.0CONCLUSION
The scope of epidemiology, its range of designs and impact on

healthcare formation and reformation has been immense. Many
healthcare - related strategies and policies that have influenced the
practice of nurses over the past century or so have been established as a
consequence of epidemiological study. Its uses also have contributed to
increasing knowledge on health care. The fact that epidemiology is seen
to be more holistic, less structured, focusing not just on individuals, but
on communities, and looks towards preventive strategies, instead of
curative ones, makes it an ideal strategy for nursing to incorporate into
its professional practice.
5.0SUMMARY
This unit has touched on epidemiology, rationale for studying the 3 ds

namely: the disease frequency, distribution and determinants as well as
the uses for the overall improvement of our health care.
ANSWER TO SELF ASSESSMENT EXERCISE 2
• Disease frequency
• Distribution and
• Determinants of diseases
6.0 TUTOR-MARKED ASSIGNMENT
Discuss five (5) importance of epidemiology
7.0 REFERENCES/FURTHER READINGS
4
K. Park (2000). Park’s Textbook of Preventive and Social Medicine: M/

s Banarsidas: India Bhanot Publishers.
Last J (1994). The Uses of Epidemiology. In Ashton J (Ed) The

Epidemiological Imagination. Buckingham: Open University
Press.
Lucas and Guiles (2003). Short textbook of Public Health Medicine for
the Tropics: 4th Edition. London: Oxford University Press.
UNIT 2 TYPES OF EPIDEMIOLOGICAL STUDIES
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CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Types of Epidemiological Studies
3.2 Observational Studies
3.2.1 Descriptive Studies
3.2.2 Analytical Studies
3.3 Experimental Studies
4.0 Conclusion
5.0 Summary
6.0 Tutor-Marked Assignment
7.0 References/Further Readings
1.0INTRODUCTION
The epidemiologist is concerned with studying disease occurrence in

people and the numerous factors which people are often exposed to that
played a significant role in disease occurrence. Thus, the epidemiologist
employs carefully designed strategies to determine this. This unit aims
at exposing you to different methods of epidemiological studies. In all, it
is crucial that you have a clear definition of the case under review and of
the person involved. Failure to obtain the required information will
make the interpretation of data difficult
2.0OBJECTIVES
At the end of this unit, you are expected to be able to:
• highlight the methods of epidemiology

• describe the importance of these methods.
3.0MAIN CONTENT
3.1 Types of Epidemiological Studies
Epidemiological studies comprises of the following:
1. Descriptive Epidemiology
a. Cross Sectional Study (Prevalence rates) with individuals as

unit
b. Longitudinal (Incidence rates)
2. Analytical Epidemiology
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a. Case-control (Case-reference) with individuals as unit of study

b. Cohort (absolute, relative, attributable risk or follow-up with
individuals as unit of study
3. Experimental/Interventional studies
a. randomized controlled trials/or Clinical trials with patients as

unit of study
b. Field trials or community intervention studies with healthy
people as unit of study
c. Community trials with communities as unit of study.
3.2 Observational Studies
This is made up of the descriptive and analytical studies
3.2.1 Descriptive Studies
This is the study of the amount and distribution of a disease within a

population by persons, place and time. The three broad questions
necessary to describe the occurrence of a disease fully relate to are:
Person - who is getting the disease (person distribution)? i.e. male or

female, the age range, ethnicity, marital status, social economic factors,
social class, education, occupation, income level, family variables such
as size, type, birth order, maternal age, parental deprivation and personal
habits.
Place - where is it occurring (place distribution)? This will answer for

region, state, district, LGA, local community, towns, village and wards
either in the city or rural areas. Boundaries are also considered with
precise location.
Time – when is the disease occurring (time distribution)? This includes

the year, season, day of the week, month and the time of the day. Certain
diseases are common during the year for example measles in dry season.
The procedures in descriptive studies are:
• Defining the population to be studied

• Defining the disease under study
• Describing the disease by: time, place and person
• Measurement of disease
• Comparing with known indices
• Formulation of an aetiological hypothesis
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The description of diseases is usually done based on some

characteristics which are shown in the table below:
Table 1: Characteristics Frequently Examined
Time Place Person

Year, season Climatic zones Age Birth order
Month, week Country, region Sex Family Size
Day, hour of Urban/rural, Marital status Height. Weight
onset Local
community
Duration Towns, Cities Occupation, Blood pressure,
and Institutions Social status, Blood
Education cholesterol and
personal habits
3.2.2 Analytical Studies
This is the second major type of epidemiological studies. While

descriptive studies looks at the entire population, analytic studies only
look at the individuals so affected within the population. The focus is
not to formulate but to test hypothesis. However, even though
individuals are evaluated in analytical studies, the inference is made in
respect of the population so selected.
Analytic studies comprises of two distinct types of observational studies,

these are: retrospective or case study and prospective or cohort
study. From here, we can determine whether or not a statistical
association exists between a disease and a suspected factor and if it
does, what is the strength of association. In prospective or cohort
studies, a group of persons are exposed to causative factors while others
are not. A follow-up is made in the nearest future to check the
proportion of effects on the exposed and the non-exposed and
comparism is then made.
SELF ASSESSMENT EXERCISE
What are the advantages and disadvantages of Cohort Studies?
Advantages Disadvantages
_________________________ _________________________
_________________________ _________________________
_________________________ _________________________
___________________________ ____________________________
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3.3 The Experimental/Interventional Studies
This is a study in which one group deliberately subjected to an

experience, is compared with a control group which has not had a
similar experience. The use of experiments in this study is done with
ethical considerations. It usually involves selection of an individual or
communities. The principle of conducting experimental trials is that
under the control of the investigator, some system are subjected to
manipulation, creating an independent variable whose effect is then
determined by the measurement of subsequent events or outcome. This
is known as dependent variable.
4.0 CONCLUSION
All the epidemiological studies complement one another. An

observational study allows nature to take its course. The investigator
measures but do not intervene. Descriptive study is limited to describing
disease occurrence in a population. Analytical goes on to examine the
relationship between health status and variables. Experimental or
interventional studies involve an active attempt to change disease
determinant or the progress of a disease. It is clearly acknowledged that
epidemiology is a major tool in the formulation and implementation of
national, regional and local health policy, providing evidence on which
policies can be based.
5.0 SUMMARY
This unit has touched on the various types of epidemiological studies

with particular reference to their importance.
ANSWER TO SELF ASSESSMENT EXERCISE
Advantages Disadvantages
a. Accurate information a. Laborious

b. Can be used to measure b. time consuming
the direct estimate c. Expensive
d. Difficulty in data
collection
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Describe the Cohort and observational studies. What are the advantages
and disadvantages of Cohort studies?
Alakija, W. (2000). Essentials of Community Health Primary Health

Care and Health Management. Medisuccess Publication
Lucas and Guiles (2003): Short Textbook of Public Health Medicine for
the Tropics 4th Edition. London: Oxford University Press.
Lucas and Guiles (1989). A Short Textbook of Preventive Medicine for

the Tropics, 2nd Edition. ELBS.
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UNIT 3 BASIC MEASUREMENT IN DISEASE

FREQUENCY
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Definition of Rate
3.2 Incidence Rates (IR)
3.3 Prevalence Rate (PR)
3.4 Other Rates
3.5 Statistics
3.5.1 Types of Statistics
3.5.2 Uses of Statistics
3.6 Data Collection
4.0 Conclusion
5.0 Summary
1.0 INTRODUCTION
The basic tool of epidemiology is the rate which relates to the number of
cases of the population at risk. In NSS 214: Introduction to Biostatistics,
you must have been introduced to different rates used in statistics. The
place of statistics which seeks to source, process and analyze data for
decision making cannot be overemphasized. In this unit, we shall be
examining in details the various data and their clinical importance.
Please follow up the discussions in this unit, with a view to understand
and see the importance of these basic measurements in disease
frequency.
2.0OBJECTIVES
At the end of this study, you are expected to be able to:
• identify the basic measurements in disease frequency

• explain the difference between each of them
• interpret the measurements for your clients care.
• describe health statistics
• distinguish between data and information
• highlight the sources of data
• describe the uses of data in nursing practice.
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3.0 MAIN CONTENT
The various basic measurements used in disease frequency are referred

to as rates. These are incidence and prevalence rates. The mode, median
and mean has been extensively discussed in NSS 214.
3.1 Definition of Rate
In defining a rate, it is important to know the number of people

(denominator) affected in the entire population (numerator) to be
multiplied by 100. Rates help to determine spread. In order to compare
populations of different sizes easily, the rate is usually expressed as the
number of events in an arbitrary total such as 1000 or 100,000.
In general, the rate is equal to the number of cases over the number of
population in a given unit of time:
: Number of cases or events X 100

Population in the same area
3.2Incidence Rates (IR)
This is the measure of the frequency of cases of disease in a particular

population, the times of onset of which occurred during a specified
period of time. Incidence rates are calculated for narrowly defined
populations (in terms of age, sex, etc.) during intervals of time as in
epidemics are often called attack rates. Attack rates are usually
expressed as a percent. A secondary attack rate is a measure of the
frequency of new cases of a disease among close contacts of known
cases. Secondary attack rates are usually calculated for household
contacts.
IR = Number of new cases X a given interval of time

Population at risk
3.3Prevalence Rate (PR)
Prevalence rate is defined as the proportion of the population affected by

a disease at a particular time. It therefore measures the number of people
in a population who have the disease at a given time.
PR = Number of existing cases Old + New X a given point in time

Total population at risk
It is clearly evident that a relationship exists between prevalence,

incidence and the duration of the disease. Prevalence is important in
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determining the work load and in planning for facilities for example the
number of hospital bed required. The relationship changes if the
incidence rate is rapidly changing, as in acute epidemic if the average
duration of illness changes in response to treatment.
Highlight the major differences between incidence and prevalence.
3.4 Other Rates to be Noted include
• Crude rate – is a rate expressed in terms of the total population. In

other words, the denominator of crude rate is the total population of
the area being studied. There are three (3) crude rates commonly
used. These are: crude birth rate, crude death rate and rate of natural
population increase.
A. Crude Birth Rate (CBR) – this is the number of life births to resident
in an area in a calendar year divided by the average population in
that population multiplied by 1000
= Total number of births in a year X 1000

Mid year population
B. The Crude Death Rate (CDR) - The total number of death in a year
divided by the mid- year population in the area multiplied by 1000.
= Total number of deaths in a year X 1000

Mid-year population
C. Rate of Natural Population Increase (RNPI) – this is the difference

between Crude Birth Rate and Crude Death Rate.
= CBR - CDR = RNPI
• Specific Rates – this is a rate expressed in terms of a sub-group of a

population (i.e.) the denominator is not the total population but a
selected portion of it. The sub-population may be defined in terms of
age or other demographic characteristics like sex, race or as a
combination. Examples are those of age, sex and cause specifics,
case fatality, and standardized rate.
Age Specific Death Rate
=Number of deaths in the aged(1-5) group X 1000

Total number of aged 1-5 in a year
Sex Specific Rate
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MMR = Number of deaths in women age group 15–44 yrs in a year X 1000
Number of women aged 15-44yrs in the population in a year
where MMR = Maternal Mortality Rate
3.5 Statistics
It is a process of collecting, processing, analyzing and reporting of data

required for planning and operating health services. Data can be
collected through primary or secondary source. The main objective is to
provide reliable, relevant, adequate, timely and unambiguous
information for health planners who will in turn interpret it for health
providers to implement.
The health of a community is assessed by data usage which serves as

indicators of the health status. The main sets of statistics are: morbidity,
mortality and service utilization statistics.
3.5.1 Types of Statistics
There are three (3) main types of statistics. These are vital, health and
morbidity statistics.
Vital statistics are statistics that records vital events such as births,
death, marriages, annulment and divorce obtained at registration centres
at Local, State and at Federal levels. The data are used to generate
information for whole groups or entire population.
Health Statistics are a combination of vital statistics and other data

pertinent to health. In the operation of health services, data can be
derived from resources and institutional records. This is can be further
explained as being derived from
• Notification of diseases which is routinely done. Diseases may be

infectious and non-infectious.
• Institutions which includes hospitals, health centres, dispensaries and
private hospitals
• Special programme like school health services, maternal and child
health, disease control programme such as Tuberculosis, Leprosy, etc
• Epidemiological survey which includes the whole population or
sample in case of an epidemic
Morbidity Statistics
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This includes data on occurrence and severity of sickness in a

community obtained from medical health service points.
Statistics from Other Sectors
There are other sectors apart from health where data can be collected to
assist in planning for health care of the people. These include:
education, public works such as housing, water supply and sanitation,
agriculture in regards to food production and distribution as well as
economic planning and development which provides the poverty and
economic indicator.
3.5.2 Uses of statistics
Statistics is used for the following among others:
• To measure the health status of the people and quantify their health
problems
• For health comparisms at local, national and international levels
• For planning, administration and effective management of health
services and programme
• For assessment of health services in relation to the set goals
• For assessing the attitudes and degree of consumers satisfaction to
health care
• For health research
3.6 Data Collection
There is a basic source of data which is of primary importance in

epidemiology. It is called CENSUS. It is so because it provides the
denominator for the calculation of race. Census is a periodic count or
enumeration of a population. It is usually done every ten (10) years.
Census is massive undertaking to contact every member of the
population in a given time and collect a variety of information. It is used
to derive population pyramid. A population pyramid is the age and sex
structure of the population displayed in the form of histogram showing
the percentage distribution of each sex at 5 yearly intervals. The primary
function of census is to provide information such as total count of
population and breakdown into groups and subgroups such as age and
sex distribution.
The data to be collected will include age, sex, colour, marital status,
relationships to head of households, occupation, housing, address, name,
educational level, parity, employment status, income, etc
Methods and Sources of Data Collection
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We shall now consider various methods of data collection. These

include:
• use of questionnaire in households

• physical examination
• special investigation
• sample registration form a population or group
• sources related to utilization services
• data collected from routine medical examination
• census
• registration of vital events
• notification of disease
• hospital records
• data from environment
• population surveys
• epidemiological surveillance
Enumeration is a key word in census. What is enumeration?

Mention the two (2) methods of enumeration
4.0 CONCLUSION
You have been exposed to epidemiological studies. It is hoped that you

understood it so well to be able to interprete and apply it in your client
management at all levels of health care. The place of data in patients’
management is of overall importance. In medical practice, a lack of
reliable data in developing countries is an important barrier to effective
management of health and other social services. It is therefore obligatory
that a viable and functional method of data collection which will assist
health planners and managers be put in place to allow for effective
implementation and evaluation of health care services.
5.0 SUMMARY
This unit has considered the various basic measurements in

epidemiology. Rate which is the basic tool for epidemiological studies
was examined with particularly reference to incidence, prevalence and
specific rates. This unit also discussed the place of statistics, its uses,
sources, types and methods of data collection. It is hoped that you will
find it very useful as you explore other variables for effective health care
of your patients and clients.
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1. Differences between Incidence and Prevalence rates
Incidence Rates Prevalence Rate

It shows the risk of acquiring a It is the rate which shows the
disease burden risk of disease or
characteristics at a given point
(point prevalence) or time (period
prevalence)
Goes usually with the same A single cross sectional study at a
population at least twice to detect point in time to show both new and
new cases old cases.
Deals only with new cases Deals with new and old cases
Aetiological factor or method of Changes do arise from low
diagnosis provide changes in incidence, and increase duration or
incidence of a disease both
Incidence of disease of insidious Almost equivalent to incidence
onset is very difficult to multiplied by average duration of
determine. Takes a long period. disease.
Useful in planning future health Useful as administrative tool
needs
Can be measured by cohort study Can be measured by cross sectional
study
a. Enumeration is the procedure employed in census to allow for

accurate head count one by one.
b. 2 methods are: defacto and dejure.
Highlight the major differences between incidence and prevalence.

Care and Health Management. Medisuccess Publication.
Lucas and Guiles (2003). Short Textbook of Public Health Medicine for
the Tropics 4th Edition. London. Oxford University Press.

MODULE 2
17
Unit 1 Strategies of Epidemiology

Unit 2 Epidemics
Unit 3 Epidemiology of Communicable and Non-Communicable
Diseases
UNIT 1 STRATEGIES OF EPIDEMIOLOGY
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Chain of Epidemiology
3.2 Disease Causation
3.3 Factors Precipitating Causation
3.4 Interrelated Factors
3.5 Levels of Prevention
4.0 Conclusion
5.0 Summary
1.0 INTRODUCTION
Your understanding of epidemiology with the 3D’s summarized (i.e.)

distribution, determinant and deterent of disease the distribution requires
some strategies which provide a search for causal association between
disease and other biological processes and specific biological
experiences. This unit will expose you to those strategies.
2.0 OBJECTIVES
At the end of this unit, the learner will be able to:
• identify the main strategies for epidemiological studies

• interpret its usefulness in disease management
• apply them in the overall health care of the patient/client.
3.0 MAIN CONTENT
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3.1 Chain of Epidemiology
The following chain exist in the study of epidemiology: These are:
• Descriptive studies: in which there is data aggregation and analysis

• Hypothesis - that is based on the result of your analysis in the
descriptive studies, you can build a model and formulate an
hypothesis
• Analytical study – the hypothesis generated in phase II is tested and
this can be either observational or experimental. Result obtained here
may suggest further studies or new hypothesis is formulated.
Chain of Epidemiology
(1)
Descriptive
(4) (2)
Further Studies Hypothesis
(3)
Analytical
3.2 Disease Causation
In disease causation, ecological factors are important. You may ask what
is ecology? Ecology is the study of relationship of organisms including
humans to each other as well as other aspects of the environment. This
has given rise to the concept of the multiple causation of disease that is
multi-factoral aetiology of disease.
There are other factors necessary for the development of disease
namely:
a. level of immunity
b. the environmental conditions
c. the agents – factors which must be present for the particular disease
to occur (i.e.) a sinequanon = without which nothing will happen.
3.3 Factors that Influence Development of the Disease
There are factors that precipitate the cause of diseases. These are the
Host factor (HF) and the Environmental Factor (EF).
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1. Host Factor: these are intrinsic factors, genetic (inborn) in a person.

It can be
• Specific (i.e.) not inborn but acquired by immunization and natural

infection
• Personality – people working hard, ambitious with strong drive
• Social Class Membership – peer grouping, organization.
Do all smokers develop lung cancer? What about those exposed to

radiation who do not develop Leukemia?
2. Environmental Factors: these are sub-divided into three namely:

biological, physical and social factors.
• Biological factors: these cause diseases that easily pass from one
person to another through direct (person-to-person) transmission or
indirect (vehicle, formites, vectors) transmission.
• Physical factors: it includes heat, light, air, water, radiation, chemical
agent, atmospheric pressure, etc.
• Social factor: this is defined as the overall economic and political
organization of a society and the institutions by which individual are
integrated into the society at various ages of their lives. Social
environment is man- made environment which includes what he has
created to make life worth living e.g. housing. It also includes the
people’s customs, levels of integration of the community, levels and
systems of medicare, the degree of enforcement of health law and
code.
3.4 Interrelated Factors
Our state of health depends on a balance of forces in a dynamic

equilibrium. If the equilibrium is precarious, then the disease occurs
easily. If the equilibrium is stable then the disease does not occur very
easily. See this ecological model showing the state of equilibrium in
disease state.
A. Ecological model ( Epidemic triangle)
Host
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Agent Environment
B. Web of Causation
Diseases do not just happen but effects depend on single isolated cases
which develop as a result of chain of position in which each link is the
result of a complex genealogy of antecedence.
Webs
If the link in the chain is broken any where, the disease may not occur.
C. The Wheel model
Wheel model tends to emphasize that the contributions of the different

components are not equal in any specific disease.
Physical
H Host
Social
Biology
It is worthy of note that the host has the genetic core and this determines
prognosis/severity. You may not know the agent of a disease before its
modification. Killing of mosquitoes may reduce the malaria episodes.
Counselling is used in Sickle Cell Disease (SCD) to reduce genetic core.
This is a way of manipulation. Manipulation sometimes leads to another
problem e.g. use of insecticide in killing mosquito. An impact
assessment is therefore necessary in carrying out a manipulation.
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Highlight the disease precipitating factors

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3.5 Levels of Prevention
Control is assumed as the ultimate aim of epidemiology but now

prevention seems taking the lead. In a narrow common usage prevention
means the inhibition of the development of a disease before it occurs but
in the broader sense. Prevention also includes all measures which
interrupt or slow the progression of disease and the resulting disability.
Prevention in epidemiology is divided into four main stages.
Stage 1 Primary Prevention
Primary prevention has two components: general health promotion

(GHP) and specific measure (SM).
GHP includes health education, environmental sanitation and good

housing SM includes chemoprophylaxis, immunization and good
nutrition.
This is the prevention stage which reduces exposure of an individual or

you alter the susceptibility of either being affected by the disease or not.
Stage 2 Secondary Prevention
The second stage is the stage of early diagnosis and treatment. Any
measure that will interfere with the progression of the disease. The
measures that constitute early detection are: screening, case finding,
mass X-ray to determine lung diseases and smear to detect cancer of
cervix in a woman.
Stage 3 Tertiary Prevention
The third stage of prevention is rehabilitation. This is the alleviation of

disabilities from the disease and attempt to restore effective functioning.
Rehabilitation can be divided into three (3) forms;
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a. Medical Rehabilitation: this is the process of medical care

aimed at developing functional and psychological liabilities of
the individual. Compensatory mechanism is put in place so as to
enable the victim to attain self dependence and live a full life.
b. Social Rehabilitation: a part of rehabilitation that aims at the

integration of a disabled person into society by helping him to
adjust to the demand of the family, community and occupation
while reducing any economic and social burden that may impede
the social rehabilitation process. It is important in diseases with
stigma such as leprosy, pulmonary tuberculosis and mental
illness. Counseling, social evaluation, individual and community
counseling, provision of services including psychiatric services,
recreation facilities are components of social rehabilitation.
c. Vocational Rehabilitation: this includes provision of those

vocational services, vocational guidance, training, selective
placements which are designed to enable a disabled person to
retain a suitable employment. He may require counseling,
vocational training, vocational evaluation, proper placement or
being looked after by others.
Stage 4 Surveillance
This is the exercise of continuous scrutiny of and watchfulness over the

distribution and spread of infection and the related factors with
sufficient accuracy and completeness to provide the basis for effective
control. This idea has three main features namely:
• systematic collection of all related data

• orderly collation and evaluation of each data
• prompt dissemination of results for action to relevant authority
The following are examples of sources of epidemiological data in the

surveillance of disease: registration of deaths, notification of disease and
reporting of epidemics, laboratory investigations, data from routine
screening e.g. blood donors, investigation of individual cases and
epidemics, epidemiological surveys, data from clinics, distribution of
the animal reservoir and the vector production and distribution and care
of vaccines, serum and drugs, demographic and environmental data and
non-medical statistics.
Objectives of Surveillance
There are two main objectives in surveillance. These are:
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• the recognition of acute problems so that immediate action is taken.

For example the recognition of an outbreak of cholera in any area so
as to “curb”/limit its spread to that area only.
• to provide broad assessment of specific problems in order to discern
long-term trends and epidemiological patterns. This is useful as basis
for planning, implementation and assessment for programme of
control and prioritization of public health programme.
4.0 CONCLUSION
You have been enlightened on the strategies which provide a search for
causal association between disease and other biological /specific
biological experiences. Host and environmental factors played a key role
in disease causation with an unparallel interrelation of the factors. The
levels of prevention are well laid out to assist you in providing the
needed support to facilitate recovery.
5.0 SUMMARY
This unit has discussed on the following: chain of epidemiology, disease

causation, factors precipitating disease causation, interrelated factors and
levels of prevention.
• Host
• Environment
• Agent
Describe the four (4) levels of prevention of illness.
Alakija, W. (2000).Essentials of Community Health Primary Health

the Tropics, 4th Edition. London: Oxford University Press.
24

the Tropics 2nd Edition. ELBS.
UNIT 2 EPIDEMICS
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Definition and Terms used in Epidemics
25
3.2 Propagation of Epidemics

3.3 Types of Spread
3.4 Investigation of Epidemics
4.0 Conclusion
5.0 Summary
1.0 INTRODUCTION
In this unit we shall be discussing epidemics and its related concepts.

While epidemics expresses the occurrence of a particular group of
illness far beyond expected nature, surveillance observes the continuous
scrutiny of and watchfulness over the distribution and spread of
infection to provide the basis for effective control. It is a hoped that you
will find it very enriching.
2.0 OBJECTIVES
At the end of this unit, the learner is expected to:
• define epidemics
• explain various terms related to epidemics
• understand the sequence of events associated with epidemics
• know how to investigate epidemic cases.
3.0 MAIN CONTENT
3.1 Definition and Terms used in Epidemics
Epidemics can be defined as the occurrence in a community or region or

a member of a defined population of a group of illnesses of a similar
nature in excess of a normal expectancy in that population.
In epidemics, any kind of disease or injury may be involved and there

are no universally applicable number of cases and no clear geographical
extent e.g. food poisoning. However, it can affect a large population.
A disease can be said to be endemic in contrast to epidemics. This is a
constant presence of a disease or an infective agent within a given
geographical area. It is the usual prevalence of a given disease within an
area.
Endemic: This is the constant presence or the usual prevalence of a

disease or infectious agent in human populations within a given
geographic area.
26
Hyperendemic is a term that expresses a persistent intense transmission

of the disease e.g. malaria
Epizootic and Enzootic are expressions that are equivalent of epidemic

and endemic as it applies to animals e.g. epizootic of yellow fever in
Monkey which precedes that of yellow fever in man. It is the incidence
of disease in animal.
Herd Immunity: this is the resistance of a group to the introduction and

spread of an infectious agent. Such resistance is based on the immunity
of a high proportion of individual members of the group and one the
uniform distribution of the immunes within the group.
Propagated-Source Epidemic: An epidemic in which infections are

transmitted from person to person or animal to animal in such a fashion
that cases identified cannot be attributed to agents transmitted from a
single source.
Epidemiologist: An epidemiologist is a person who applies

epidemiologic principles and methods to the prevention and control of
disease.
3.2 Propagation of Epidemics
Epidemics only affect a susceptible number of populations. There is an

incubation period before manifestation of symptoms; however,
susceptible may develop inapparent infection. The infectious agent may
leave the host during the communicable period which varies in timing,
and duration with each disease. The following are the sequence of
events:
• introduction of the agent

• attack on susceptible
• acquisition of immunity
• reduction in the number of susceptible
• decline of the epidemic
Introduction attack on acquisition of decline number

of the agent susceptible immunity of
susceptible
DECLINE
* The Epidemic Cycle
27
However it is worth noting that the cycle described above can be

influenced by any of these factors namely: immunity decline, migration
and birth/death.
3.3 Types of Spread
There are two major types of spread in any epidemic. These are
common vehicle epidemic and latent case. We shall consider each of the
spread turn by turn.
3.3.1 The Common Vehicle Epidemic
This is also called the point source. Transmission here may be through
water, food, air or by inoculation. When the epidemic results from a
single exposure of the population it is called a point source epidemic.
Sometimes there may be repeated multiple exposure or a continued
exposure over a period of time e.g. a contaminated well (point source).
It is a point source at the closing up and if from the closing up there is
continuous drinking from the source (contaminated well), then it
becomes a multiple source.
Characteristics of Common Vehicle Epidemics
• explosive in onset
• limited in time, place and person (i.e.) there is geographical
limitation
• serial transfer or propagation : this usually involves a transfer from
host to host. The spread can be by contact, direct or indirect between
the infected and susceptible.
• Route is respiratory, oral-fecal or genital
(1)
Epidemic Curve
Epidemic Curve
Cases
28 Time
(Median incubation period)
The Index Case
This is the first among a number of similar cases which are

epidemiologically related. Index cases are often identified as a source of
contamination or infection. Typically, a common vehicle epidemic
shows a rapid rise and a fall within one incubation period whereas in
propagated epidemic new cases continue to develop beyond one
incubation period.
Please note the followings
• that a typical point source epidemic may be affected by the

development of secondary source. For example, water that is infected
gives diarrhea.
• by the continuous contamination of the source, it ceases to give the
picture of point source but multiple sources.
• a disease that has a long incubation period will give the type of a
long epidemic curve with serial transfer.
• on the other hand, a propagated epidemic may look highly infectious
with short incubation period.
• geographical mapping can be done to determine the geographical
location of the victims and a spread can occur from centre to sub-
boundary regions. The geographical marking and epidemic curve can
help determine the type of epidemic and the source.
Clearly differentiate between index case and common vehicle onset

---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------
3.4 Investigation of Epidemic
Having being exposed to some details of epidemics, it must be stated

clearly that there are due processes for investigating epidemics and these
must be done systematically. They include the following:
1. Verification of the diagnosis: this includes what type of disease is

been viewed, full history, laboratory investigation, post mortem
29
examination may be required but often a clinical assessment is all

that is needed.
2. Confirmation of the existence of an epidemic. This is done by:
• looking at the previous clinical records and data, questioning the

local people in order to obtain approximate estimate of the previous
incidence of the disease in the area.
• Do a mapping. An epidemic curve to see the number rising, a map to
show that cases are spreading.
3. The identification of the affected persons and their characteristics:

who is affected? in terms of age, sex, name, occupation, etc. Obtain
their recent movement, time of onset of their symptoms, find out
whether they were previously immunized, and find out their contacts
within the incubation period of the disease so that you will be able to
follow the contact. Here also, you will endeavor to look for
additional cases that may be concealed and not typical in nature.
Identify a common experience shared by all of those affected e.g. do
they all go to the same venue when they ate the food (ceremonies)?
Was the water contaminated from source or a sick person visited the
family of recent? All of these provides for epidemiological
description of those affected.
4. Conduct further laboratory and immunological investigation of the

population. Carriers are deduced e.g. cholera, cerebro-spinal
meningitis to identify the type of organism and therapy sensitivity.
5. Study the environmental conditions at the time of the outbreak and

compare with the previous condition. Find out if there is any change
in water source, weather, food, housing conditions, population of
human beings and any environmental change for epidemic invasion.
6. Formulate an hypothesis. Here you will want to find out how it

started, its source, method of transmission, reservoir, etc.
7. Management of the cases affected. This is done in any of the
following:
• Treatment of cases by health personnel

• Rehabilitation facilities. Measures are taken to prevent spread and
control of epidemics. These will include chemotherapies,
immunization, isolation of infected individuals, and imposition of
quarantine so as to reduce movement from one point to the other as
well as education of the community to obtain cooperation.
Permanent control measures are also put in place which includes any
of the following: personal hygiene, health education, water supply,
30
vector control, food hygiene legislation, continuous vaccination

programme.
• Report writing. This is usually from a layman, health planners and a
scientific report.
• Continued surveillance of the population for early detection to
reduce the spread.
4.0 CONCLUSION
An epidemic is an unusual occurrence in a community of disease or

specific health related behaviour that is in excess of expected
occurrence. The techniques and methods of surveillance can be applied
not only to communicable diseases but also non-communicable disease
such as environmental hazards, cancer and other degenerative diseases
as well as and social problems such as drug addiction.
5.0 SUMMARY
This unit has considered the subject epidemics. We examined the

various components of epidemics, propagation, spread, characteristics
and methods of investigating epidemics.
In common vehicle onset is explosive; limited in time, place and person

(i.e.) there is geographical limitation, serial transfer or propagation and
usually involves a transfer from host to host. In Index case the spread
can be by contact, direct or indirect between the infected and
susceptible, route is respiratory, oral-fecal or genital, transmission here
may be through water, food, air or by inoculation.
Clearly differentiate between index case and common vehicle onset.
Mulhall A (1996). Epidemiology, Nursing and Healthcare: A New

Perspective. London: Macmillan.
Park K. (2000). Park’s Textbook of Preventive and Social Medicine: M/

s Banarsidas: Bhanot Publishers, India
Valanis B (1992). Epidemiology in Nursing and Health Care. Second

Edition. Connecticut: Appleton & Lange.
31
WHO (2000). Communicable Diseases 2000. WHO/CDS/2000.1.WHO,

Geneva.
UNIT 3 EPIDEMIOLOGY OF COMMUNICABLE AND

NON-COMMUNICABLE DISEASES
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Definition
3.2 Agents Causing Diseases
3.2.1 Agents and Disease Caused
32
3.2.2 Infectious Agents

3.2.3 Reservoir
3.3 Concepts in Communicable Disease
3.4 The General Methods of the Control
3.5 Overview of Non-Communicable Diseases
3.6 The Risk Factors of Non-Communicable Diseases
3.7 Problems of Investigating Non-Communicable Diseases
4.0 Conclusion
5.0 Summary
1.0 INTRODUCTION
The epidemiology of communicable disease is an important aspect of

this course. You will remember by hindsight the place of who, what,
where, and when in the understanding of epidemiology. To this end,
therefore, the relationship of epidemiology, communicable and non-
communicable disease will form the basis of our discussion in this unit.
2.0 OBJECTIVES
At the end of this unit, the learner is expected to be able to:
• define communicable and non-communicable diseases

• identify various agents causing diseases
• describe infectious agents
• enumerate the concepts that applied to communicable and non –
communicable disease
• discuss the general methods of control of communicable and non-
communicable diseases disease
• enumerate problems of investigating non-communicable disease
• discuss the significant changes in the health and disease pattern.
3.0 MAIN CONTENT
3.1 Definition
A communicable disease is an illness that occurs due to a specific

causative agent or its toxic products which arises through transmission
of that agent or its products from a reservoir to a susceptible hosts either
directly as from an infected person or animal or indirectly through an
intermediate plant or animal host, vector or the inanimate environment.
3.2 Agents Causing Diseases
33
We shall now consider some of the key points in the definition above
3.2.1 Agents and Disease Caused
Agents Disease Caused

Viruses Measles, small pox,
Ricketsiae Typhus organism and tapeworm
Bacteria Spirochetes – Syphilis
Fungi Candidiasis, Tinea Capitis,
Histoplasmosis
Protozoa Malaria, Trypanosomiasis,
Amoebiasis
Nematodes: roundworms,
guineaworms, onchocerchiais:
Helminthes Trematodes and Cestodes:
Schizomiasis, Paragomiasis, Flat
worms, Tapeworms, Tinea Sadinasa
Anthropds Gigar
3.2.2 Infectious Agent
Infectious agent is any organism or agent that is capable of producing

infection or infectious diseases. Infection is the successful invasion of
the body by micro organisms. You have discussed this extensively in
NSS 314: Applied Sciences for Nurses. Please note that infection is not
the same as infectious disease and contamination because infection can
be apparent or manifest.
Differentiate between infection and contamination

__________________________________________________________
__________________________________________________________
__________________________________________________________
3.2.3 Reservoir
A reservoir is any human being/animal/anthropod/plants/soil or

inanimate matter in which an infectious agent normally lives and
multiply and on which it depends primarily for survival and reproduces
itself in such manner that is can be transmitted to a successive host. Man
is the only reservoir of infection of many diseases: (man to man).
Occasionally an animal may serve as the reservoir and this is called
Zoonosis.
34
A zoonosis is an infectious disease transmissible under natural

conditions from vertebrae animal to man. For example rabies,
trypanosomiasis, yellow fever (jungle type), anthrax, Lassa fever from
rat and tape worm.
3.3 Concepts in Communicable Disease
The following concepts are very important in understanding

communicable disease
• Incubation Period: this is the period between the exposure to an

infectious agent and the appearance of the first signs and symptoms
of disease.
1st stage of Typical

illness period
Acute
illness
(a) (b)
(c) (d)
Incubation Period Prodromal Stage
Exposure
It is worthy of note here that the (d) point is the variable. Here the
patient can go into convalescence, chronic illness or death can occur.
• Characteristics that Influence Diseases/Illness Formation
There are characteristics that influence disease/illness formation in the

body. These are:
- Infectivity
- Pathogenicity
- Virulence
- Antigenic power
What is the meaning of the following terms?
Infectivity__________________________________________________
Pathogenicity_______________________________________________
Virulence__________________________________________________
Antigenic Power___________________________________________
• Resistance
35
This is the sum total of body mechanism that provides a barrier to the
progress of invasion or multiplication of infectious agents and damage
their toxic products. This is made possible through immunity.
• Carrier
A carrier is someone who though has disease causing organism in his

body but do not show any sign of infection. The carrier has the ability to
harbour and disseminate the parasite without showing any clinical
evidence of infection. There are times when even carriers of a disease
are more than those showing the signs of the disease. They often
become chronic carriers but this does not last long. Some of the disease
known to have carriers include: cholera, salmonella typhi, poliomyelitis
and diphtheria.
Types of Carrier
1. Incubatory carrier is one that is transferred during incubation period

2. Convalescent carrier is one that is transferred during recovery period
3. Intermittent carrier is one that is on and off
4. Chronic carrier is one in which the individual keeps carrying the
disease on for a long time
5. Healthy carrier is someone who does not show the manifestation at
any time but keeps on transmitting it to people.
• Immunity
This is the resistance usually associated with possession of antibodies

having specific actions on the micro-organism concerned with a
particular infectious disease or its toxin. An individual is considered
immune when he possesses specific protective antibodies or cellular
immunity as a result of previous infection or immunization or by
previous experience.
Immunity can be natural or acquired. Natural is inherent in the
individual or specie and it is independent of previous infection.
Acquired also can be active and passive. Active acquired immunity can
be natural or induced, while passive acquired may be
natural/transplacental or passive induced.
Active Immunity: this is the immunity an individual develops as a

result of infection or specific immunization and usually associated with
antibodies or cells having a specific action on the disease or toxin. This
can be acquired through any of the following:
• After infection e.g. measles
36
• After in apparent infection e.g. poliomyelitis

• After immunization with an antigen which may be killed vaccine.
Passive Immunity: this is the transference of antibodies produced in

one body to another to induce protection against disease. This is useful
for individual who cannot form antibodies or for the normal host who
takes time to develop antibodies after active immunization. Here the
body depends solely on ready-made antibodies. This can be derived
from any of the following:
• when an antibody is administered

• transfer of maternal antibodies across the placenta
• transfer of lymphocytes to induce passive cellular immunity.
Herd Immunity: this is the level of resistance of a community or group

of people to a particular disease. It provides an immunological barrier to
the spread of disease in the human herd.
• Vaccine: this is an immuno-biological substance designed to

produce specific protection against a given disease. It stimulates the
production of protective antibody and other immune mechanisms. It
may be prepared from live modified mechanism or inactivated or
killed organisms.
3.4 The General Methods for the Control of Communicable

Disease
Preventive Control of Epidemic International

measures patient, contact measures measures
and
environment
(a) Vaccination (a) Measures Measures to (a) control of
against epidemic designed to limit spread of international
prevent spread communicable travelers,
(b) Chlorination of of infection disease which immigrant, goods,
water supplies matters to has developed animal products
(c)Pasteurization person and to widely in a and the means of
of milk the environment group or transport of the
37
(d) Control of (b) Keeping community above

rodent arthropod, contacts under within an area, (b)
animal surveillance state or nation: Intergovernmental
(e) Immunization during (a) Notification arrangement,
(f) Public health incubation of occurrence to national laws
education periods the appropriate (c) Monitoring
(g) Improvement (c) Keeping health authority immunization
of environmental records under (b) Mass posts especially at
sanitation and control until immunization the boarders and
personal; hygiene found to be free (c) Health ports.
(h) of infectious education
Chemoprophylaxis agents (d) Source and
e.g. malaria, (d) reporting to contact
filariasis, local authority investigation
meningococcal (e) Isolation
meningitis, (f) Concurrent
bacillary disinfection
dysentery. (g) Quarantine
i.e. limitation of
improvement of
person exposed
to infection
(h)
Immunization
of contact
(i) Investigation
of contact
(j) Specific
treatment
Adapted from “Essentials of Community Health, PHC and Health
Management
3.5 Overview of the Non-Communicable Diseases
Non – communicable disease is an illness that occurs due to a specific

causative agent or its toxic products but not transferable from persons to
persons. It may be acute or chronic. Our discussion here will cover the
chronic diseases. This will include all ailments or deviation from normal
which have one or the following characteristics:
• Permanent disability
• leaves residual disability
• caused by non-reversible pathological change
• it requires the special training of the patient for rehabilitation
38
• it may be expected to require a long period of supervision,

observation and care.
With the control of communicable disease in some part of the world, a

change occurs in the demographic picture leading to an older
population. This is why chronic disease has become the commonest
cause of morbidity and mortality. Non-communicable diseases include
cardiovascular, renal, nervous and mental diseases, musculo-skeletal
conditions such as arthritis and allied diseases, chronic non-specific
respiratory diseases (e.g. chronic bronchitis, emphysema, and asthma),
permanent results of accidents, senility, blindness, cancer, diabetes, and
obesity and various other metabolic and degenerative diseases and
chronic results of communicable diseases. Disorders of unknown cause
and progressive cause and often labeled “degenerative”.
3.6 The Risk Factors of Non-Communicable Diseases
There are six (6) major key sets of risk factors that are responsible for
major distribution of non-communicable disease in relation to its
morbidity and premature mortality. These are:
• use of cigarette and other forms of smoking

• alcohol abuse
• failure or inability to obtain preventive health services e.g.
hypertension control, cancer detection and management of diabetes
• life-style changes e.g. dietary patterns, physical activity
• environmental risk factors e.g. occupational hazards, air and water
pollution and possession of destructive weapons
• stress factors
3.7 Problems of Investigating Non-Communicable Disease
There are some problems in the understanding of the natural history of

chronic/non-communicable disease investigation which invariably
results in difficulties in causal investigation and research.
1. Absence of a known agent. The absence of a known agent makes

both diagnosis and prevention difficult. An example of this is
cancer.
2. The multifactoral nature of the aetiology because most chronic

diseases are caused by multiple factors. There is rarely a simple
one-to-one cause-effect relationship and in the absence of a
39
known agent, the term “risk factor/s is used to describe certain

factors in relation to a person’s background or lifestyle.
Occasionally it can result from cumulative effects of multiple
factors and may be addictive or synergistic.
3. Long latent period (incubation period) between the first exposure

to suspected cause and the eventual development of disease
which is often difficult to determine. It is assumed that what is
happening now to someone may result from the effect of past
happenings.
4. Indefinite onset so that the incidence rate is difficult to calculate.

Most chronic disease is slow in onset and development and the
distinction between diseased and non-diseased states may be
difficult to establish. An example of this is cancer which by the
time the patient seeks medical attention, the damage would have
been irreversible or difficult to treat.
5. The differential effect of the factors on the incidence and the

cause of the disease.
What are the risk factors for hypertension?

__________________________________________________________
__________________________________________________________
__________________________________________________________
4.0 CONCLUSION
The prevalence of chronic disease reveals an upward trend all over the
world and for obvious reasons; this trend is likely going to increase.
Some of the adduced reasons are: that life expectancy is increasing with
a greater number of people living to older ages and are at risk of chronic
diseases of various kinds relative to ageing, changing life-style and
behavioural patterns that are favourable to onset of chronic diseases and
modern medical care has enabled chronic disease sufferers to survive.
However, the impact of the disease on the lives of the people is serious
when measured in terms of loss of life, disability, family stress, poverty
and its resultant effect on the nations economy.
5.0 SUMMARY
We have discussed this unit covering the definition, agents causing

disease. Infectious agents, reservoir, concepts worthy of note in the
discussion of communicable disease and the general methods of the
40
control. Here we also examined the chronic non-communicable diseases

which are assuming higher increase among young and adult population
in both developed and developing countries with attending changing
patterns in health and disease.
Infection is the successive invasion of micro organisms in the body.
Contamination is the presence of living infectious agents on exterior

surfaces of the body or upon articles or apparel or solid articles.
Infectivity means ability of the micro organism to colonize an individual

Pathogenicity means ability to cause adverse effect
Virulence means causing severe measure
Antigenic is the ability to elicit antigenic response from the host
Non-modifiable risk factors: age and genetic factors

Modifiable factors: obesity, salt intake, saturated fats, alcohol, physical
activity, environmental stress
Other factors: secondary hypertension resulting from the use of oral
contraceptives, noise, vibration and temperature.
1. Differentiate between infection and contamination.

2. What are the risk factors for hypertension?

Last J (1994): The uses of Epidemiology. In Ashton J (Ed). The

Epidemiological Imagination. Buckingham: Open University
Press.
the Tropics, 4th Edition. London: Oxford University Press.
41

MODULE 3
Unit 1 Sexually Transmitted Infection

Unit 2 Human Immuno-Virus/Acquired Immune Deficiency
Syndrome
Unit 3 Demographic Incidence and Prevalence of HIV/AIDS
Unit 4 Testing for HIV and Results
Unit 5 Prevention, Treatment and Control of the HIV/AIDS
UNIT 1 SEXUALLY TRANSMITTED INFECTIONS
42
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 What are Sexually Transmitted Infections?
3.2 Types of Sexually Transmitted Infections
3.3 Consequences of Sexually Transmitted Infections
3.3.1 Health Consequences
3.3.2 Social consequences
3.3.3 Economic Consequences
4.0 Conclusion
5.0 Summary
1.0 INTRODUCTION
Communicable diseases are sometimes classified by way of

transmission. The same applies in case of sexually transmitted
infections. Even when Sexually Transmitted Infections are
predominantly transmitted through sex, you should note that there are
situations where sex is not directly involved. For example, the unborn
baby can contract gonorrhoea from the womb. The issue of HIV is
another example. Aside from sex, you must have learnt that HIV can be
transmitted through other means like the exchange of blood and other
bodily fluids (through the sharing of infected body- piercing
instruments; transfusion with infected blood and blood products e.t.c)
and also from mother to child. This can occur during pregnancy, during
birth or through breast-feeding if the mother is infected with HIV. In
this unit, you will learn more about Sexually Transmitted Infections.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
• define Sexually Transmitted Infections

• give examples of some common Sexually Transmitted Infections
• list the characteristics of at least two Sexually Transmitted
Infections.
3.0 MAIN CONTENT
3.1 What are Sexually Transmitted Infections?
43
Sexually Transmitted Infections are bacterial, viral, and parasitic

infections, transmitted through sexual contacts. They usually affect the
genital areas. They may also cause serious disease complications to the
body.
Sexually transmitted infections were, over the years, known by some

other names. They used to be called venereal diseases (VD). This name
was purportedly derived from the Roman goddess of love. Later, the
name changed to sexually transmitted diseases (STDs).
In recent times, the name Sexually Transmitted Infections is used. This

is because it has been found that not all infections will get to the stage of
disease. An example is the HIV infection. The fact that someone is
infected with HIV does not mean he would eventually contract AIDS.
But that is if he/she manages the condition very well through adequate
diets, rest and medication.
3.2 Types of Sexually Transmitted Infections
There are many organisms transmitted through sex and that can lead to
diseases. You will learn about three of them in this unit.
1. Gonorrhoea
This is caused by a bacterium called Neisseria gonorrhoea. It is

transmitted through intercourse and by oral-genital and anal-genital
contact. There is need for warmth and moisture provided by the mucus
membranes of the vagina, mouth, or anus for the Neisseria gonorrhoea
to survive. Because of this, it is not too likely for you to contract
gonorrhoea by sharing someone else’s towel or from sitting on a public
toilet seat, unless the bacterium had just been deposited there. Even
then, the place should be warm and moist.
2. Syphilis
The organism that causes syphilis is called Treponema pallidum. It is a

corkscrew-like organism, which resembles bacteria.
Like the gonorrhoea bacterium, the organism causing syphilis can

survive only in the warmth and moisture by the mucous membranes of
the human body. The organism dies quickly outside the body. For this
reason, syphilis may not be contracted from a toilet seat. Syphilis can be
detected through a simple blood test.
3. Genital Herpes
44
There are two types of herpes simplex viruses. Type 1 result in cold
sores in the mouth, while Type Two causes genital herpes. In about two
to 10 days after the virus has entered the body, some symptoms begin to
appear. The symptoms include sores and swollen glands (around the
groin). The person will also experience flu-like symptoms (fever,
muscle aches and a sick feeling). Also, pain in the genital area during
urination or intercourse may occur. There may also be fatigue, swelling
of the legs and watery eyes. The treatment of syphilis is handled
medically.
List 3 types of Sexually Transmitted Infections and organisms

responsible for them
1a--------------------------------------- 1b-------------------------------
2a--------------------------------------- 2b-------------------------------
3a--------------------------------------- 3b-------------------------------
3.3 Sexually Transmitted Infections and Consequences
Case Study: Awaiting Result
Miss X, a young school leaver, contracted gonorrhea while awaiting her

school certificate examination result. Instead of going to the hospital,
she discussed the problem with her friends, who gave her some drugs to
use. Because her condition was not improving, she borrowed some
money and decided to go to a hospital far away from her home. In the
hospital, treatment was commenced. On her third appointment in the
hospital, she met a nurse who was from the same town with her. This
made her to abandon her treatment.
1. What made Miss X to abandon her treatment?

2. Explain the possible effect of the lady’s half-treated gonorrhea?
3. What do you think should be done to prevent this type of action
among young girls?
3.3.1 Health Consequences
Sexually transmitted infections can have a lot of implications on the

reproductive health of an individual. Especially in women, the
45
consequences can be very serious. This is why STIs should be properly

treated.
In women, pelvic inflammatory disease (PID) can come with the

following associated complications:
- Infertility, ectopic pregnancy leading to maternal mortality;

chronic pelvic pain, and increased possibility of subsequent
pelvic infections.
- Adverse pregnancy and neonatal outcomes have also been

identified as a consequence of STIs. In pregnant women, the
organism responsible for syphilis, Treponema palludum can cross
the placenta barrier and infect the foetus. The same is possible
with gonorrhoea and chlamydia trachomatis.
3.3.2 Social Consequences
In a country or an area where much value is attached to children, the

social consequences of STI can be serious for a woman. Imagine a
situation where improperly managed STI leads to infertility. A lot of
sad things can happen to the woman:
- She will be stigmatized;

- She can be abandoned or rejected by her husband;
Even when there is no problem of infertility, when there is STI, there

may be conflicts arising between the couples. The friends and family
members who provide support may start accusing the woman. There is
mistrust. This may lead to both psychological and emotional problems
for the couple.
3.3.3 Economic Consequences
STIs are not without some economic consequences. Handling the

situation involves both direct and indirect costs. The direct costs are
costs incurred in the process of treatment. Diagnosis, screening and
treatment can be very expensive. Because of the expensive screening
cost, some communities have resorted to the use of syndrome
management or presumptive therapy without laboratory screening. Some
costs cannot be measured in Naira and Kobo, but that does not mean that
they do not exist. Some of the indirect costs associated with STIs
46
include: loss of productive life, the cost in infant morbidity, debility and
mortality, increase in the economic burden placed on a society.
4.0 CONCLUSION
Sexually Transmitted Infections can be prevented and can also be

treated. If they are not treated properly, they can have serious
implications for the sexual health of an individual. There is the need to
acknowledge that other STIs such as gonorrhea, syphilis, Pelvic
Inflammatory Disease, etc should be given attention like HIV. When
these infections are not properly treated, they can cause a lot of harm.
5.0 SUMMARY
In this unit, you have learnt that Sexually Transmitted Infections are
infections one can get through sexual intercourse. But you also know
that one can get Sexually Transmitted Infections through other means
apart from sex.
In the past, venereal diseases (VD) and sexually transmitted diseases

(STDs) were used to describe this class of infections. Examples of
Sexually Transmitted Infections are gonorrhea, syphilis and genital
herpes. You have learnt in this unit the various consequences of sexually
transmitted infections. You are already aware that the consequences of
STIs go beyond physical pain or discomfort. There are also cordial and
economic consequences, all of which can have adverse effects on the
well being of the individual.
Gonorrhoea: This is caused by a bacterium called Neisseria

gonorrhoea.
Syphilis: The organism that causes syphilis is called Treponema
Pallidum. It is a corkscrew-like organism, which resembles bacteria.
Genital Herpes. There are two types of herpes simplex viruses. Type
One results in cold sores in the mouth. Type Two causes genital herpes.
1. Explain sexually transmitted infections with two examples.

2. Explain the health implications of STIs.
3. Differentiate between direct and indirect cost of STIs.
Greenberg et al (1997). Wellness: Creating a Life of Health and Fitness,

pp. 119-125. London: Allyn & Bacon.
47
Dullabetta et al (eds). Control of Sexually Transmitted Disease. U.S.A:

AIDSCAP.
UNIT 2 HUMAN IMMUNO-VIRUS/ACQUIRED

IMMUNE DEFICIENCY SYNDROME
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 HIV/AIDS
3.2 Different Types of HIV
3.3 The Structure of HIV
48
3.4 Replication in HIV

4.0 Conclusion
5.0 Summary
1.0 INTRODUCTION
HIV is Human Immuno-deficiency virus (HIV) and AIDS is Acquired

immune Deficiency Syndrome. As a syndrome AIDS is a group of signs
and symptoms resulting from the attack of the HIV on the body’s
Immune system.
It is the worst epidemic so far and it affects every part of the globe. Its
effect is estimated to e that of four world wars put together and it still
defies cure. Available drugs do not cure but prevent multiplication of the
virus.
2.0 OBJECTIVES
At the end of this unit the learner should be able to:
• define HIV/AIDS
• describe the symptoms of HIV/AIDS
• explain the different types of HIV
• differentiate the different types of HIV on the basis of cytopathy and
virulence.
• describe the structure of HIV
• explain the different genes and their functions in the HIV genome
• explain all the processes involved in the replication of HIV.
3.0 MAIN CONTENT
3.1 HIV/AIDS
The Human Immuno-Deficiency Virus (HIV) is a retro virus so called

because this single stranded RNA (ssRNA) virus contains a polygene
that codes for a reverse transcriptase. The HIV is causative agent of the
Acquired Immune Deficiency (AIDS) which is a pandemic that have
spread to the whole world. In 1981, the Communicable Diseases Centre,
Atlanta USA noted an increase in requests to use pentamidine for
Pneumocystis carinii infection in previously well individuals who also
suffered severe infections by other normally harmless microorganisms.
49
These included Candida albicans oesophagittis, mucocutaneous herpes

simplex, toxoplasma CNS infection or pneumonia and cryptosporidial
enteritis; and Kaposi’s sarcoma was often present. Such patients had
evidence of impaired immune function as shown by skin test anergies
and depletion of CD4 positive T–helper lymphocytes. This
immunodeficiency syndrome appearing in an individual without a
known cause, such as treatment with immunosuppressive drugs was
referred to as “Acquired Immune Deficiency Syndrome” (AIDS).
Signs and symptoms of acute HIV infection usually occur within days to
weeks after initial exposure and last from a few days to more than 10
weeks (usually less than 14 days). Unfortunately, the syndrome is often
undiagnosed or misdiagnosed because HIV antibodies are not usually
detected during this early phase of infection.
AIDS is a severe, life threatening syndrome which represents the late

clinical state of infection with HIV. Invasion and destruction of helper T
– cells lead to suppression of the patients immune system. The immune
system of the HIV infected person is unable to produce antibodies in
response to T – cell dependent antigens. Secondary infections cause by
viruses, protozoa, bacteria and or fungi become systemic and caused
death of the patients. AIDS patients die as a result of overwhelming
infections caused by a variety of opportunistic pathogens. Previously
considered to be a universally fatal disease, certain combinations of
drugs referred to as cocktail are used in extending life of AIDS patients.
Different Types of Human Retroviruses
HIV is classified as a retrovirus because it contains’ reverse

transcriptase. It is a D type virus in the Lentivirus family. Retroviruses
are ribonucleic acid (RNA) viruses and in order to replicate they must
make a deoxyribonucleic acid (DNA) copy of their RNA. It is the DNA
genes that allow the virus to replicate.
Like all viruses, HIV can replicate only inside cells, commandeering the
cell machinery to replicate (reproduce). However, only HIV and other
retroviruses, once inside the cell, use the enzyme called reverse
transcriptase to convert their RNA into DNA which can be incorporated
into the host cells’ gene.
Infections of cultured T – cells with HIV usually result in cell death. The
major antigenic types (HIV–1 and HIV–2) have been identified and are
readily distinguished by differences in antibody reactivity to the
envelope glycoproteins. The two HIV types share approximately 40%
genetic identity. There is some disagreement about whether or not they
50
are pathogens. Both apparently cause AIDS, but some researchers think
that HIV–2 is less virulent in causing diseases.
Different isolates of HIV–1 and HIV–2 exhibit considerable genomic

variation and antigenic heterogeneity. This type of variation is observed
in HIV isolates obtained from individuals over the course of their
infection. HIV strains often display differences in replicative capacity
and cytopathic effect /cytopathicity.
In 1983, the causative virus of AIDS, HIV was isolated from blood
lymphocytes and recognized as belonging to the Lentivirus (slow
viruses) group of retroviruses related to similar agents in monkey and to
similar virus in sheep and goats.
Table 1: Human Retroviruses
Virus Characteristics
HTLVI endemic in W. Indies and SW Japan transmission via blood
human milk, can cause adult T–Cell leukaemia and HTLV
1 associated myelopathy and tropical spastic apararesis,
HTLV2 Uncommon, sporadic, occurrence, transmission via blood
can cause hairy T. Cell leukaemia
HIV 1, HIV2 Transmission via blood, sexual intercourses responsible
for ARC, AIDS, AIDS dementia etc. HIV 2 is West
Africans in origin. closely related but antigenically distinct
Human Causes foamy vacuolation in infected cells, little is known
foamy virus of its occurrence or pathogenic potential.
Human Detected in placental tissues by electron microscopy and
placental by the presence of reverse transcriptase
virus(es)
Human Nucleic acid sequence representing endogenous
genome retroviruses are common in the vertebrate genome, often in
viruses well defined genetic loci, acquired during evolutionary
history, not expressed as infections virus; function
unknown, perhaps should be regarded as mere parastic
DNA.
The human placental and genome viruses are not known to be infectious
agents.
An increasing number of different strains of both HIV – 1 and HIV – 2

are being identified by molecular virology and by phenotyping in cell
culture. Highly cytopathic and infectious strains of HIV – 1 have been
identified in parts of Central Africa. Increases in virulence appear to be
due to minor differences in the molecular structure of the virus. Some
strains of HIV – 2 appear to cause few symptoms in those known to
have been infected for many years.
51
The molecular biological evidence through nucleic acid sequencing

indicates that both HIV – 1 and the closely related HIV – 2, seen in
West African probably arose from closely related primate viruses. HIV
– 1 may have been present in humans in Central African for many years
but in the late 1970s it began to spread rapidly possibly with change of
properties, as a result of increased transmission following major socio –
economic upheavals and migration of people from Central to East Africa
such as female prostitutes and mobile male soldiers.
3.3 The Structure of HIV
The general structure of HIV is similar to that of Human T– cell

Leukemia viruses (HTLV), the virus consists of an external lipid bilayer
glycoprotein envelope (including envelopes proteins gp 120 and gp 41),
an internal protein core (proteins p15, p17 and p24) a viral RNA
complexed with reverse transcriptase. The HIV genome is
approximately 10 kilobases which is larger than the HTLV. In addition
to the structural gag, pol and env genes and regulatory lat (analogous to
HTLV rex) genes (nef, rif, vpu and vpr). HIV -2 does not have
sequences for vpu but does encode a novel gene, vpx that is also found
in the simian Immunodeffiency virus.
A complete HIV particle consists of an envelope, a coat or capsid shell

and core. The envelope is the membrane that surrounds the virus. It is a
lipid (fat bilayer), which is derived from the host proteins. Embedded in
the envelope is the viral encoded glycoprotein (gp), gp41, bound to this
is the outer glycoprotein knob gp120 molecules bind to specific
molecules on the surface of the host cell called cluster designation 4
(CD4) receptors. The capsid is the protein coat that surrounds the core
(viral genome) of the virus. It is made up of protein (P) p17 and p18
which the icosahedral symmetry. The viral core is the elongated inner
mass of the virus which contains two identical single strands of viral
RNA, structural protein, the enzyme reverse transcriptase and other
enzymes. The main core protein is P25. Serological diagnosis of HIV is
based on P24, P26 specific detection of antibodies to HIV and envelope
proteins.
i. List the different types of HIV

.......................................................................................
.....................................................................................
ii. What are the Lentiviruses?
iii. The enzyme used in classifying HIV is
3.4 Replication in HIV
52
Viral replications are regulated by the products of the genes. The

replication cycle is often halted after integration of the provirus, so that
the infection remains latent in the cell. The lat and ref genes, for instance
function as transactivating factors and can increase production of viral
RNAs and proteins when latently infected cells are stimulated to
differentiate (e.g. T-helper cell by antigen) or stimulated by infection
with certain other viruses (e.g. HSV, cytomegalovirus)
The life cycle of HIV involves 8 steps namely:
• Attachment / Entry
• Reverse transcription and DNA synthesis
• Transport to the nucleus
• Integration
• Viral transcription
• Viral protein synthesis
• Assembly of virus
• Release of virus
1. Entry of HIV into Cells
Infection typically begins when an HIV particle, which contains two

copies of the HIV RNA, encounters a cell with a surface molecule called
cluster designation 4(CD4). Cells carrying this molecule are known as
CD4 positive cells.
One of the more of the virus pg120 molecules bind tightly to CD4
molecules (s) on the cells surface. The binding of gp 120 to CD4 results
in conformational chance in the gp 120 molecule allowing it to bind to a
second molecule on the cell surface known as co-receptor. The envelope
of the virus and the cell membrane then fuse, leading to the entry of the
virus into the cell. The gp41 of the envelope is critical to the fusion
process. Drugs that block either the binding or the fusion process are
being developed and tested in clinical trials.
Studies have identified multiple co-receptors for different types of HIV

strains; these co-receptors are promising targets for new anti – HIV
drugs, some of which are now being tested in pre-clinical and clinical
studies. In the early stage of HIV diseases, most people harbour viruses
that use, in addition to CD4, a receptor called CCR5 to enter their target
cells. With disease progression, the spectrum of co-receptor usage
expands in approximately 50 percent of patients to include other
receptors, notably a molecule called CXCR4. Virus that utilizes CCR5 is
called R5 HIV and virus that utilizes CXCR4 is called X4 HIV.
53
Although CD4+ T – cells appear to be the main target of HIV, other

immune system cells with and without CD4 molecules on their surfaces
are infected as well. Among these are long – lived cells called
monocytes and macrophages, which apparently can harbour large
quantities of the virus without being killed, thus acting as reservoirs of
HIV. CD 4 T – cells also serve as important reservoir of HIV. : a small
proportion of theses cells harbours HIV is a stable, inactive form.
Normal immune processes may activate these cells resulting in the
production of new HIV virions. Cell to cell spread of HIV also can
occur through the CD 4 – mediated fusion of an infected cell with an
uninfected cell.
2. Reverse Transcription
In the cytoplasm of the cell HIV reverse transcriptase converts viral

RNA into DNA, the nucleic acid form in which the cell carries the
genes.
Nine of the 15 antiviral drugs approved in the United States of America

for treatment of people with HIV infection, AZT, ddC, ddI, d4T, 3TC
nevirapine, delavirdine abacavir, and efavireng- work by interfering
with this stage of the viral cycle.
3. Integration
The newly made HIV DNA moves to the cell’s nucleus, where it is
spliced into the list’s DNA with the help of HIV intergase. HIV DNA
that enters the DNA of the cell is called a “provirus” intergase is an
important stage for the development of new drugs.
4. Viral Transcription
For a provirus to produce new viruses, RNA copies must be made that
can be read by the host cell’s protein making machinery. These copies
are called messenger RNA (mRNA) and production of mRNA is called
transcription, a process that involves the host cell’s own enzymes. Viral
genes in concert with the cellular machinery control this process, the lat
gene for example encodes a protein that accelerates transcription.
Genomic RNA is also transcribed for later incorporation in the budding
virion. Cytokines proteins involved in the normal regulation of the
immune response may also regulate transcription. Molecules such as
tumour necrosis factor (TNF) – alpha and interleuckin6 (IL – 6),
secreted in elevated levels by the cells of HIV – infected people may
help to activate HIV proviruses. Other infections, by organisms such as
Mycobacterium tuberculosis, may also enhance transcription by
inducing the secretion of cytokines.
54
5. Translation
After HIV mRNA is processed in the cell’s nucleus, it is transported to

the cytoplasm. HIV proteins are critical to this process. For example, a
protein encoded by the rev gene allows mRNA encoding HIV, structural
proteins to be transferred from the nucleus to the cytoplasm. Without the
rev protein, structural proteins are not made. In the cytoplasm, the virus
co-opts the cell’s protein making machinery including structures called
ribosome – to make long chains of viral proteins and enzymes using
HIV mRNA as a template. This process is called translation.
6. Assembly and Budding
Newly made HIV co-reproteins, enzymes and genomic RNA gather just
inside the cell’s membrane while the viral envelope proteins aggregate
within the membrane. An immature viral particle forms and buds off
from the cells, acquiring an envelope that includes both cellular and HIV
proteins from the cells membrane.
During this part of the viral life cycle, the core of the virus is immature
and the virus is not yet infectious. The long chains of the proteins and
enzymes that make up the immature viral core are now cleaved into
smaller pieces by a viral enzyme called protease. This step results in
infectious viral particles. Drugs called inhibitors interfere with this step
of the viral life cycle. Six of such drugs are saquinavir, ritonavir,
indinavir, amprenavir, nelfinavir and lopinavir –have been approved for
marketing in the United States of America.
4.0 CONCLUSION
In this unit, we presented a definition of HIV/AIDS. Specifically, we

saw that HIV is Human Immuno-deficiency virus (HIV) and AIDS is
Acquired immune Deficiency Syndrome. As a syndrome AIDS is a
group of signs and symptoms resulting from the attack of the HIV on the
body’s Immune system. Hope you enjoyed your studies.
5.0 SUMMARY
We have seen that HIV, the aetiology of AIDS which is pandemic is

retrovirus of the Lentivirus family. HIV/AIDS is associated with
opportunistic infections such as Pneumocystic carinii infections,
Candida albicans oesophagitis, toxoplasma CNS infection etc. HIV
infected patients had evidence of impaired immunity as shown by skin
test allergies and depletion of CD4 positive T-helper lymphocytes.
There are two types of HIV i.e. HIV 1 and HIV 2 on the basis of
antibody reactivity to the envelope glycoproteins both share 70%
55
genetic identity. The general structure of HIV I is similar to that of

HTLV. The viral replication is regulated by the product of genes. Eight
steps are involved in HIV replication which includes attachment/entry,
reverse transportation and synthesis, transportation to the nucleus,
integration, viral transcription, protein synthesis assembly and release of
viruses. Careful and in-depth examination of patients is required so as
not to miss out something vital in clinically diagnosing HIV.
i. What do you understand by HIV and AIDS?

.......................................................................................
.......................................................................................
.......................................................................................
ii. List six infectious agents associated with AIDS.
.......................................................................................
.......................................................................................
iii. What effect has HIV on the T – cell?
i. Different types of HIV are…HIV 1 and HIV 2

ii Lentiviruses are (slow viruses) group of retroviruses related to
similar agents in monkey and to similar virus in sheep and goats
iii. The enzyme used in classifying HIV is…reverse transcriptase
Baron S. (1996). Medical Microbiology 4th Edition, pp. 761-776: The

University of Texas Medical Branch at Galveston.
Burton R.W. Engelkirk P.G., (2000). Microbiology for the Health

Sciences, 6th edition. pp. 309 – 412 Lippincott Williams &
Wilkins.
56
Moro, D.D., Opere, B.O. and Famurewa, O (2004). HIV Infection

among Pregnant Women in Osogbo, Osun State, Nigeria Nig. J.
Res.Rev. Sci. 3:234 – 239.
UNIT 3 DEMOGRAPHIC INCIDENCE AND

PREVALENCE OF HIV/AIDS
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
57
3.1 HIV/AIDS Global Demographic View

3.2 The UN’s View of HIV/AIDS Pandemic
3.3 HIV/AIDS Epidemic in Nigeria
3.4 HIV Sentinel Surveillance in Nigeria
3.5 Epidemiology of HIV/AIDS in Nigeria
3.5.1 HIV Prevalence by State
4.0 Conclusion
5.0 Summary
1.0 INTRODUCTION
This aspect of your study deals with demography which is the statistical
study of human population. This course unit essentially will relate HIV/
AIDS prevalence and incidence to the epidemiology of the disease. That
is, the study of HIV/AIDS in terms of its distribution pattern or spread
and the number of new cases around.
2.0 OBJECTIVES
By the end of this unit you should be able to.
• understand the factors that encourage the spread of AIDS in

Africa
• appreciation of the spread of HIV/AIDS globally and locally
• know HIV surveillance epidemiology in terms of modes or routes
of transmission
• identify some high risk culture – related practices/ factors that
increase HIV/AIDS spread.
3.0 MAIN CONTENT
3.1 HIV/AIDS Global Demographic View
The disease spreads through infected blood production and drug abuse,
but overwhelmingly by sexual contact, predominantly between men and
women. Women are more vulnerable to infection due to physiological
and social reasons, and sex workers are far more likely than the
population at large to be infected. But the sexual behaviour of men is
largely responsible for spreading the disease. The study of HIV/AIDS
general distribution pattern or spread as well as the total number of new
cases is shown in the alarming figures enumerated below according to a
report by the World Health Organization (WHO)
1. North America ________________ 1.2 Million
58
2. Caribbean ________________ 300, 000

3. Western Europe ________________ 220,000
4. Eastern Europe & Central Asia _____________ 1.6 Million
5. East Asia ________________ 870,000
6. South & South East Asia ________________ 74, Million
7. Oceania ________________ 74,000
8. Sub-Sahara Africa ________________ 25.8 Million
9. North Africa & Middle East _______________ 510,000
10 Latin America _______________ 1.8 Million
39.774 Million
Highlight the possible reasons for the difference in the total population
of HIV positive people in North America and Sub-Saharan Africa.
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3.2 The United Nations’ View of HIV/AIDS Pandemic
The United Nations has called AIDS the most devastating disease
mankind has ever faced. AIDS is a worldwide catastrophe and the
biggest plague in human history. The latest statistics tell us that around
40 Million people worldwide are HIV- positive. In sub-Saharan Africa,
we have 70% of that 40 Million people. Experts estimate that 600,000
people, especially babies become infected each year.
All the wars in the twentieth century resulted in 33 million deaths. But
in just about 25 years of AIDS, already about 25 million people or more
have died, 8,000 people die every day from HIV/AIDS in sub-Saharan
Africa, from Nigeria to Cape Town, 6,000 people die daily from AIDS.
The continent of America and the world were shocked when on

September 11 of the year 2001, the world trade centre collapsed through
terrorist’s attacks, but in Africa, the world trade centre collapses twice a
day, in terms of the number of victims that die from AIDS in Africa.
3.3 Epidemic of HIV in Nigeria
The spread of this virus in Nigeria is believed to have started in the

1980s with the first AIDS case reported in 1986. Nigeria is currently
experiencing a generalized HIV prevalence persistently above 1% in
pregnant women attending antenatal clinics since 1999. In 2003, it was
estimated that 3.2 – 3.8 Million persons were living with HIV/AIDS in
Nigeria.
59
It is believed that statistics on HIV/AIDS in Nigeria is not a true picture

of what is on ground but it is estimated that there could be 1 to 2 Million
people in Lagos alone who are HIV positive. The city of Lagos is also
estimated to have the largest number of HIV positive victims than many
cities in the world. It is said that, in Lagos, commercial hawking of
one’s body is a big factor in HIV/AIDS spread. According to the Federal
Ministry of Health, the official HIV/AIDS prevalence rate in Nigeria
between 2000 to2005 is around 5.8%, and more recently, the 2007
health statistics indicates 4.4%, hopefully a steady and promising
decline.
3.4 HIV Sentinel Surveillance
The virus sentinel surveillance was established to monitor trend in the

HIV epidemic and assess the impact of the response. The survey was
conducted from August 29 to November 26, 2005 to determine HIV
prevalence among pregnant women attending antenatal clinics and also
acquire data for estimating and projecting HIV Figures and trends in the
general population.
The 2005 sentinel survey involved 36,931 pregnant women attending

antenatal clinics in 160 sites (86 urban and 74 rural) in 36 states and the
management Team was set up by the Federal Ministry of Health under
the chairmanship of the Director of Public Health. The National Action
Committee on AIDS (NACA), UN agencies, bilateral agencies and other
stakeholders participated as members of the committee.
3.5 Epidemiology of HIV/AIDS in Nigeria
The prevalence of HIV among antenatal clinic clients after the 2005
sentinel survey was found to be 4.4% it was 1.9% in 1991, 4.5% in
1996, and 5.8% in 2001. HIV epidemic in Nigeria has since extended
beyond the high risk groups to the general population. Some parts of the
country are worst affected than others but no state community is
unaffected. All the states of Nigeria have a generalized epidemic (>1%
among pregnant women) The epidemic in the country can be described
as heterogeneous with various communities in different stages, some
declining while others are still rising.
From the result of the 2003 survey, it was estimated that 3.5 million
people were living with HIV/AIDS in the country. The report also
showed that HIV was more prevalent in the 20-29 years age group in the
urban areas and amongst persons with only primary and secondary
school education. AIDS cases are becoming more visible in
communities. Although AIDS case reporting has been characterized by
60
under – recognition, under – reporting and delayed reporting, the

number of reported cases has been on the increase especially since 1996.
HIV prevalent rate among commercial sex workers in Nigeria has

remained high and on the increase from 17.5% in 1991. Through 22.5%
in 1993, to 35.6% in 1995. This group constitutes an important reservoir
of HIV infection for transmission to the general population through
sexual networking. Also the growth in prevalence among tuberculosis
patents has remained relatively high 2.8% in 1991, 7.9% in 1993 13% in
1995 and 17% in 2000 (refer to figures 1 to 3 and tables 1 to 4).
3.5.1 HIV Prevalence by State
States in the North West and South West presents Lower HIV
prevalence. High HIV prevalence is concentrated in Benue and
adjoining State (see Figure 1).
Figure 1: Geographical Distribution of HIV Prevalence by State

(HSS 2005)
HIV Prevalence by State (Nigeria 2005)
61
The state HIV prevalence range from 1.6% (Ekiti) to 10.0% (Benue) and
the median prevalence was 4.0% (Abia)
Figure 2: HIV Prevalence by State, (HSS 2005)
62
2005 HIV SENTINEL SURVEY.
3.4.3 HIV Prevalence by Marital Status (Table)
*HIV Prevalence was Lowest among Married Women
63
Table 1: HIV Prevalence by Marital Status (HSS 2005)
Marital Sample Number Prevalence Confidence

Status Size Positive (%) Interval
Single 1648 78 4.8 3.8-6.0
Married 35074 1528 4.4 4.1-4.6
Other 182 16 8.8 5.1-13.9
Total 36904 1623 4.4 4.2-4.4
Table 2: HIV Prevalence by Educational Status
Educational Sample Number Prevalence Confidence

None 3757 156 4.2 3.5-4.9
Quranic Only 5816 181 3.1 2.7-3.6
Primary 7768 375 4.8 4.4-5.3
Secondary 13650 689 5.0 4.7-5.4
Higher 5911 222 3.8 3.3-4.3
Total 36902 1623 4.4 4.2-4.6
Table 3: HIV Prevalence by Gravidity and Parity (Table)
HIV prevalence among those in their first pregnancy was higher than
those women with two or more pregnancies. The difference however
was not statistically significant. HIV prevalence was also higher among
women with no previous deliveries compared to women with one or
more deliveries.
Table HIV Prevalence by Gravity and Parity
Marital Sample Number Prevalence Confidence

1 9532 445 4.7 4.3-5.1
2 or more 27317 1177 4.3 4.1-4.6
Total 36851 1622 4.4 4.2-4.6
Parity
0 10332 490 4.7 43.-5.2
1 7672 388 5.1 4.6-5.6
2 or more 18699 737 3.9 3.7-4.2
Total 36703 1615 4.4 4.2-4.6
3.4.4 Trend Analysis
Figure 3: National HIV Prevalence Trend, 1991 – 2005, (HSS 2005)
64
Figure 4 shows the trend of HIV prevalence in Nigeria between 1991

and 2005, as reported from the HIV sentinel sero–surveillance cycle.
There was a steady increase in HIV prevalence from 1.8% in 1991 to
5.8% in 2001 before a drop to 5.0% in 2003. The result for 2005 showed
a further drop to 4.4%.
Table 4: HIV Prevalence Trends by State from 1991 – 2005, (HSS

2005)
State 1991/92 1993/94 1995/96 1999 2001 2003 2005
Adamawa 0.3 1.3 5.3 5.0 4.5 7.6 4.2
Anambra 0.4 2.4 5.3 6.0 6.5 3.8 4.2
Benue 1.6 4.7 2.3 16.8 13.5 9.3 10.0
Borno 4.4 6.4 1.0 4.5 4.5 3.2 3.6
Cross River 0.0 4.1 1.4 5.8 8.0 12.0 6.1
Delta* 0.8 5.1 2.3 4.2 5.8 5.0 3.7
Edo 0.0 1.8 3.0 5.9 5.7 4.3 4.6
Enugu 1.3 3.7 10.2 4.7 5.2 4.9 6.5
Kaduna 0.9 4.6 7.5 11.6 5.6 6.0 5.6
Kano 0.0 0.4 2.5 4.3 3.8 4.1 3.4
Kwara 0.4 2.4 1.7 3.2 4.3 2.7 2.8
Lagos 1.9 6.8 - 6.7 3.5 4.7 3.3
Osun* 0.0 1.4 1.6 3.7 4.3 1.2 2.0
Oyo* 0.1 0.2 0.4 3.5 4.2 3.9 1.8
Plateau* 6.2 8.2 11.0 6.1 8.5 6.3 4.9
Sokoto 1.8 1.6 - 2.7 2.8 4.5 3.2
Abia ND ND ND 3.0 3.3 3.7 4.0
Akwa Ibom ND ND ND 12.5 10.7 7.2 8.0
Bauchi NN ND ND 3.0 6.8 4.8 3.4
Bayelsa ND ND ND 4.3 7.2 4.0 3.8
4.0 CONCLUSION
65
It is clear from the WHO report of demographic incidence and prevalent

study earlier mentioned with regards to HIV/AIDS ravaging effect on
the whole world with new cases springing up left, right and centre. All
hands must be on deck in the fight to control the scourge that has been
on the increase ever since its emergence.
5.0 SUMMARY
In this unit we understood that the latest statistics tell us that there are
about 40 Million HIV positive people globally. 70% of the 40 Million
sero-positive people are said to be in sub-Saharan Africa alone 600,000
people mainly babies become infected with HIV every year. In just
about 25 years of AIDS 25 Million people or more have died of it in the
world. 8000 people die everyday of AIDS in sub-Sahara Africa alone
and the 2003 sentinel survey estimated that about 5.0 Million people are
living with HIV/AIDS in Nigeria.
Describe the global demographic view of HIV/AIDS and the nursing

intervention.
Adeyi .O. Kanki, P.I; Odutolu, O and Idoko, J. A (2006), Aids in

Nigeria: A Nation on the Threshold. U.S.A: Harvard University
Press.
Technical Report (2005). National HIV/Syphilis Sero-Prevalence

Sentinel Survey among Women attending by Dept of Public
Health, National AIDS/STI Control Programme.
FMOH (1992). Care of a Person with AIDS in the Community. Lagos:

Federal Ministry of Health and Social Services.
UNIT 4 TESTING FOR HIV AND RESULTS
66
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 The HIV test
3.2 Testing Infants for HIV
3.3 Possible HIV Test Results
4.0 Conclusion
5.0 Summary
1.0 INTRODUCTION
In this unit, we will look at various ways of examining HIV, testing

infants for HIV, possible HIV test results, and the window period.
2.0 OBJECTIVES
At the end of this unit, you should be able to:
• describe HIV testing

• describe testing infants for HIV
• identify possible HIV test results.
3.0 MAIN CONTENT
3.1 The HIV Test
The HIV test is a test that tells if a person is HIV positive or negative by
using a simple blood test or at times making use of saliva or urine.
Several methods have been developed to detect the infection. Most HIV
test that are readily available and affordable do not actually test for the
HIV virus but rather for the antibodies produced by the body in reaction
to the HIV infection. It is important to note that even though HIV
antibodies can be detected in the mouth and in urine, the virus cannot be
transmitted from one person to another through saliva or urine. This is
because there is not enough of the virus in saliva or urine to infect
people this way. HIV needs to be present in very large quantities in
order for a person to be infected. The only body fluids that contain
enough HIV to be infectious are blood, semen, vaginal fluids and breast
milk. There are tests which can detect the virus but they are very
expensive to carry out and require rigorous procedure to carry it out.
It is important to remember that the HIV test can only detect if a person
has contracted the virus or not:
67
• If a person has AIDS (only a doctor can make this diagnosis)

• How the person became infected with HIV
• How long the person has been living with HIV
• Who infected the person
HIV test can be carried out in any reputable Medical institution/facility

and various approved and regulated Non Governmental Organisations
and Laboratories across the country. When the HIV test is carried out
typically it is followed by another HIV test which is called a
confirmatory test, which is done to confirm the result of the first test. A
confirmatory test is carried out only for positive HIV results and it is
carried out shortly after the first test so as make sure that the positive
result is a truly positive result.
3.2 Testing Infants for HIV
Children born to HIV positive mothers can be prevented from contacting

the virus from their mothers with proper medical attention, care and
treatment. Unfortunately it is difficult to ascertain if a child is positive or
not soon after it is born, this because children carry their mothers
antibodies for several months after birth as a form of protection against
infection. Since most available HIV test seek to detect HIV antibodies
then the children would test positive because they are carrying their
mothers HIV antibodies. Babies born to HIV positive mothers can test
positive for antibodies acquired from their mothers for as long as 15
months after birth for this reason, identifying infected and uninfected
infants can only be possible after 18 months. HIV-antibody test results
will only show us infants who have been exposed to the virus via their
mothers. As mentioned previously, in environments where the HIV test
which can detect the virus itself as opposed to the HIV antibody
produced by the mothers body is available, the children can accurately
be tested HIV negative or positive.
When the HIV test is carried out typically it is followed by another HIV
test which is called___________________________________________
3.3 Possible HIV Test Results
68
A. Negative Result
An HIV negative result can mean one of the following things…….
The person has not been infected with the HIV virus and the HIV
antibodies have not been found in the individual’s blood.
That person has been infected with HIV in the last 3-6 months, and the
body has not yet developed antibodies for the HIV test to detect the
infection. It is recommended that everybody who is HIV negative
should be asked to carry out another HIV test within 3-6 months of the
first test during which time they should avoid putting themselves and
others at risk contracting the HIV infection. This period is called the
window period.
In cases where an individual has developed AIDS and is very ill, the
person’s HIV test may read HIV negative this usually happens close to
the death of the person.
The Window Period
This refers to the period between when a person is first infected with
HIV and the development of HIV antibodies in the person’s body. If an
individual gets tested for HIV during this period it will read negative.
This is what is called a false negative because the individual is actually
positive but the test cannot detect it yet because the body has not
produced enough antibodies for the test to detect. During this period
though the person has tested negative the person is actually HIV positive
and can infect other people. In other words, a person is actually infected
with HIV but the test will show up negative.
Depending on the test used, it can take anywhere from three weeks to 6
months for the antibodies to show up in the blood. Almost all people
(99%) develop antibodies within 3 months, however. Some testing sites
now have more sophisticated tests that are able to “shorten” the window
period. In other words, they can detect antibodies within a much shorter
period of time -- approximately 25 days after infection.
If this new test is not available, a person who has received a negative
test result and has recently engaged in risky behaviour should be tested
again 3-6 months after the last time they participated in a risky activity
(For example, if s/he had unprotected sex one month ago, s/he should be
tested again in 2-5 months).
B. Indeterminate Result
69
This means that it is not possible to tell if the person has been infected
with HIV based on the test results. In other words, the test results are
inconclusive meaning it does not indicate either a negative or a positive.
This does not occur very often, but it can happen to people with any of
the following conditions:
• multiple pregnancies or miscarriages

• multiple blood transfusions
• received an organ transplant
• Suffer from other autoimmune diseases, such as lupus or Grave’s
Disease
• kidney disease or are receiving dialysis treatment
• liver disorders
• some type of cancer.
• in the process of Sero-Conversion from negative to positive (window
period)
• Cross reactivity due to prior inoculating, e.g. anti viral vaccine
• Prior medical conditions, e.g. auto immune disorders and severe
Kidney diseases
• People who receive indeterminate results should also be re-tested
again in six months if they have engaged in HIV risk behaviours.
C. Positive Result
A positive result means that the HIV antibodies have been detected in
the person’s blood and that the person has been infected with HIV and
can infect others through exposing them to infectious body fluids
(blood, semen, vaginal fluids or breast milk). All positive results are
confirmed with another test called a confirmatory test. Therefore, it is
unlikely that a positive result will be false.
D. False Positive Result
There are sometimes a positive result will be obtained when there are no
HIV antibodies in the blood. These can be due to a number of reasons
such as:
Technical errors: Technical errors which may be made by the laboratory

scientist.
Serological cross-reactivity, repeated freezing and thawing of the HIV

test reagent.
Stickiness of stored sera in malaria

E. False Negative Result
70
This situation occurs when the blood tested gives a negative result for
HIV antibodies while it should have tested positive as the person is
infected. The reason for this is the Window period, that is the person
must have been newly infected or the test maybe defective
4.0 CONCLUSION
In this unit, we summarized that HIV test is a test that tells if a person is
HIV positive or negative by using a simple blood test or at times making
use of saliva or urine. We also illustrated that children born to HIV
positive mothers can be prevented from contacting the virus from their
mothers with proper medical attention, care and treatment. A review of
possible HIV test also includes: negative result, indeterminate result,
positive result, false positive result and false negative result.
5.0 SUMMARY
This unit provided a broad view of HIV testing and possible HIV
results. Let us attempt the questions below.
Describe the Indeterminate and False HIV test results.
Anne-Marie B. and Chris Y. (2002). Understanding Health. SAGE.
Allot, M and Robb, M. (1997). Understanding Health and Social Care.

SAGE.
D’Cruz P. (2004). Family Care in HIV. SAGE.
McKee N. Bertrand and Becker-Benton A. (2004). Strategic

Communications in the HIV/AIDS Epidemic. SAGE.
UNIT 5 PREVENTION, TREATMENT AND CONTROL

OF THE HIV/AIDS
71
CONTENTS
1.0 Introduction
2.0 Objectives
3.0 Main Content
3.1 Rationale for Combination Therapy
3.2 Combination Therapy
3.3 Other Pharmaceutical Care Services
3.4 Preventive Measures for Target Group
3.5 Preventive Measures for Medical Personnel
3.6 Preventive Measures for the General Public
3.7 Care for those Already Infected with HIV/AIDS
4.0 Conclusion
5.0 Summary
1.0 INTRODUCTION
This unit is the second part and complementary to the first one on HIV/
AIDS treatment, leading to the advent of combination therapy.
Combination therapy as the name implies comes as a follow up to
antiretroviral therapy because of certain problems due to the use of
antiretroviral drugs, chief among which are toxicity and resistance. The
virus is also capable of constant mutation thus the need for combination
therapy.
2.0 OBJECTIVES
At the end of this unit, you are expected to:
• know what combination therapy is all about in HIV/AIDS

treatment
• understand the rationale for combination therapy
• familiarize with other pharmaceutical care services
• appreciate the different preventive measures for target groups.
3.0 MAIN CONTENT
3.1 Rationale for Combination Therapy
A) Combination therapy is useful in increasing efficacy through

addition and/or synergistic antiviral activity.
B) To reduce the toxic effects associated with each drug used at
higher doses.
72
C) To delay the emergence of drug resistance and/or broaden

coverage against pre-existing drug resistant virus.
D) To target virus in different cellular reservoirs and/or different
tissue reservoirs and direct treatment towards cells at different
stages of activation
3.2 Combination Therapy
1) Retrovir (AZT)/ Epivir (3TC) combination. It gives pronounced

and prolonged fall in HIV RNA Load. It also gives marked and
sustained increase in CD4 cell counts.
Dosage:
Retrovir 200mg t.i.d
Epivir 150mg b.i.d
2) AZT/3TC/indinavir combination
Review the rationales for combination therapy

i. _____________________ ii. _________________
iii. _____________________ iv. _________________
3.3 Other Pharmaceutical Care Services
1) Drug information for AIDS patients: Information on new drugs

and therapies. Medical literature, newsletters, computer bulletin
etc must be available to all concerned.
2) Protection of patients: It is the ethical and legal responsibility of
the pharmacist and others involved in AIDS patient’ care, to
protect their confidentiality
3) Counseling of HIV patients: Counsel patients from time on the
use of medical devices and appliances.
Example:
i) Use of condoms, made of latex as more effective barrier to virus

than lambkin or natural membrane that is porous.
ii) Adding the use of spermicide to a condom may provide
additional protection
iii) It is safer to use condom with lubricant
iv) Community services
73
All health providers involved in the care of HIV/AIDS patients should

provide needed information to the patients and others in the community,
including those who do not have AIDS.
Lastly, due to many problems of treatment especially toxicity, there is

therefore need to emphasize prevention which is often said to be safer
and cheaper than cure.
3.4 Preventive Measures for Target Group
These are measures that essentially apply to risk groups such as long
distance truck drivers, prostitutes, youths, intravenous drug users,
market women and medical personnel.
1) Maintain regular and faithful sex partners. Do not share partners

or engage in group sex.
2) Avoid patronizing commercial sex workers. The highest
percentage of HIV/AIDS cases has been reported with this group.
3) Always use condom if you must have casual sex but do not rely
onit. The tensile strength of some of these condoms is inadequate
because of our tropical environmental condition. A sizeable
number of them tear during use. More-over the pore sizes are
much larger than the largest viral particle; hence do not offer
absolute protection against HIV infection.
4) Do not share injection needles or other surgical appliances. Insist
on fresh ones.
5) Do not patronize unqualified medical personnel for injection,
tattooing, circumcision and scarification. If you must do any of
the above, provide your own blades or surgical equipment.
6) Request and insist that your traditional medical practitioners use
fresh blades or other incision instruments when any cut, or
incision or scarification is to be done.
7) Insist that your barber disinfect his barbing instruments before he
applies them on you.
8) Do not donate blood if you have engaged in risky behaviours.
3.5 Preventive Measures for Medical Personnel
• Assume that all blood, blood products and other body products and
other body fluids are infectious and adopt measures to prevent direct
contact with them.
• Sterilize all re-useable needles and syringes, surgical and skin
piercing instruments after use
• Screen all blood for HIV before transfusion. It is worthwhile to
maintain this standard in all situations so as to ensure safety
74
• Wash your hands with soap and disinfect after any accidental
exposure to blood, semen, vaginal secretions and body fluids
• Wear hand gloves during vaginal examinations, blood, dental
procedures etc
• Decontaminate all re-usable instruments immediately after use, then
disinfect or sterilize them.
• In case of accidental cuts, or needle stabs, wash the area thoroughly
with soap and disinfect with suitable and effective agents.
• Spills of body fluids and blood should be well cleaned using suitable
disinfectants such as preparations containing chorine
• Wash your hands with soap and water after working with a patient
and before you start with another patient.
• Avoid blood transfusion to patients except in critical cases and where
there are no alternatives/options
3.6 Preventive Measures for the General Public
General preventive and control measures are needed for the general
public and the main interest here are to:
• prevent HIV infection

• prevent and control cross-infection
• reduce the personal and social impact of HIV and care for those
already infected
• preventive measures for the general populace are designed to prevent
the spread due to ignorance
3.7 Care for Those Already Infected with HIV/AIDS
1) Information, Education and Awareness Creation
The above three are the key to AIDS prevention. It is only through
enlightenment information that people can voluntarily and individually
decide to change some of their risk behaviours. It should be remembered
that such behaviours are private and often known to the individual alone.
The media must be fully involved in the dissemination of information to

the general public and not AIDS victims alone.
75
Enumerate the HIV/AIDS preventive measures for the general public
i. ______________________ ii. ___________________
iii. _______________________ iv. ___________________
2) Health and Social Services for Patients
Information and education programmes alone do not sustain prevention.

A supportive social environment and health services must be put in
place especially for those already inflected.
The HIV infected individual needs counseling so also their sexual

partner and family. A supportive social environment such as tolerance,
avoidance of discrimination towards the infected individual at the
workplace and at home, helps to protect and give assurance to the
victim. There is no health rationale for the isolation of HIV/AIDS
patients. What the HIV patients need is empathy, understanding and not
pity. Actually, existing prejudices serve to scare people from
volunteering for HIV screening. Certain health and social services such
as counseling of I.V drug users, provision of free sterile needles and
syringes to I.V drug users during the period of counseling and drug
withdrawal, supply of drugs free or at subsidized rates to strengthen
people’s capacity to make long term behaviour changes are helpful.
Treatment with drugs is a very crucial and integral part of HIV/AIDS

control and in line with the National Drug Policy launched in 1990 It is
absolutely necessary to make available at all times, drugs which are very
effective, affordable, safe, and of good quality in all sectors of health
care through the rational use of drugs.
4.0 CONCLUSION
There is thus need for behavioural change as high rates of sexual contact
with multiple partners is also incriminated in AIDS spread. There is
therefore greater need for awareness creation and effective mobilization
of human, material, medicinal and financial resources towards effective
control of the AIDS scourge.
5.0 SUMMARY
Due to the adverse effects of the ART drugs, particularly toxicity,

combination therapy is preferable and in vogue. There are other care
services for treatment of HIV/AIDS victims and these include
counseling, drug information and community services. There are also
76
preventive measures in place which include those targeted at specific

groups such as the commercial sex workers (CSW), medical personnel,
HIV/AIDS patients and the general public.
Highlight the adverse effects of antiretroviral drugs.
FMOH (1992). Care of a Person with AIDS in the Community. Lagos:

Nigeria Federal Ministry of Health and Social Services
TDR News (2007). “Enhancing Drug Discovery for Neglected Tropical

Diseases”. Geneva: WHO.
UNAIDS (2001). Sources and Prices of Selected Drugs and Diagnostics

for People Living with HIV/AIDS. Geneva: WHO.
77

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NSS 305 EPIDEMIOLOGY IN NURSING

3.1 Definition of Epidemiology

Epidemiology is the study of the distribution and determinants of health-

Although dismissed by most scientists of the time, this finding and

SELF ASSESSMENT EXERCISE 1

Highlight the three important component of epidemiology

• For planning and evaluation of health care

SELF ASSESSMENT EXERCISE 2

Using at least 3 out of the reasons in 3.2 above, discuss among

3.3 Uses of Epidemiology

1. Understanding the causation of the disease and the development of

However, epidemiology is used for the following:

• To analyze the respective role of agent, host and the environment in

• To help the to complete the clinical features and natural history of

The scope of epidemiology, its range of designs and impact on

This unit has touched on epidemiology, rationale for studying the 3 ds

ANSWER TO SELF ASSESSMENT EXERCISE 2

6.0 TUTOR-MARKED ASSIGNMENT

Discuss five (5) importance of epidemiology

7.0 REFERENCES/FURTHER READINGS

K. Park (2000). Park’s Textbook of Preventive and Social Medicine: M/

Last J (1994). The Uses of Epidemiology. In Ashton J (Ed) The

UNIT 2 TYPES OF EPIDEMIOLOGICAL STUDIES

The epidemiologist is concerned with studying disease occurrence in

At the end of this unit, you are expected to be able to:

• highlight the methods of epidemiology

3.1 Types of Epidemiological Studies

Epidemiological studies comprises of the following:

a. Cross Sectional Study (Prevalence rates) with individuals as

a. Case-control (Case-reference) with individuals as unit of study

a. randomized controlled trials/or Clinical trials with patients as

3.2 Observational Studies

This is made up of the descriptive and analytical studies

3.2.1 Descriptive Studies

This is the study of the amount and distribution of a disease within a

Person - who is getting the disease (person distribution)? i.e. male or

Place - where is it occurring (place distribution)? This will answer for

Time – when is the disease occurring (time distribution)? This includes

The procedures in descriptive studies are:

• Defining the population to be studied

The description of diseases is usually done based on some

Table 1: Characteristics Frequently Examined

Time Place Person

3.2.2 Analytical Studies

This is the second major type of epidemiological studies. While

Analytic studies comprises of two distinct types of observational studies,

SELF ASSESSMENT EXERCISE

What are the advantages and disadvantages of Cohort Studies?

3.3 The Experimental/Interventional Studies

This is a study in which one group deliberately subjected to an

All the epidemiological studies complement one another. An

This unit has touched on the various types of epidemiological studies

ANSWER TO SELF ASSESSMENT EXERCISE

a. Accurate information a. Laborious

6.0 TUTOR-MARKED ASSIGNMENT

7.0 REFERENCES/FURTHER READINGS

Alakija, W. (2000). Essentials of Community Health Primary Health

Lucas and Guiles (1989). A Short Textbook of Preventive Medicine for

UNIT 3 BASIC MEASUREMENT IN DISEASE