MODULE 6

PUBLIC HEALTH
PUBLIC HEALTH c. Increase food requirements - childhood, adolescence,
pregnancy, sickness
the science and art of preventing disease, prolonging life, and
promoting physical and mental health and efficiency thru: 3. Population problem
Organized Community Effort for: 4. Person's lifestyle
the sanitation of the environment
the control of community infections 5. Iatrogenic disease
the education of the individual in principles of personal
hygiene II. DISEASE CAUSATION AND NATURAL HISTORY OF DISEASE
the organization of medical service for the
early diagnosis and treatment of diseases THREE ECOLOGIC FACTORS OF DISEASE
the development of a social machinery which will ensure
a standard of living adequate for 1. Agent
the maintenance of health any element, substance, or force whether living or non-living,
the presence or absence of which can perpetuate a disease.
Agencies set to carry out organized community health
activities: TYPES:

1. Voluntary a. Living
private, supported wholly or in large part by non-tax funds plant and animals (bacteria, fungi, molds, yeast, arthropods,
e.g., NGOs, private clinics, private foundations helminths, protozoan)

2. Governmental b. Non-living
public, official or tax supported e.g., government hospitals, Physical and Mechanical agents extremes in temperature,
health centers, district hospitals light, electrocution, physical trauma
Chemical agents:
I. HEALTH AND DISEASE exogenous common poisons
endogenous - toxic products of metabolism
WHO definition of Health
c. Nutrient
state of complete physical, mental, and social well-being not deficiency or excess is bad
merely the absence of disease and infirmity
2. Host
comprehensive rather than physical
qualitative than quantitative a vertebrate or invertebrate capable of getting infected by
dynamic rather than static and exposed to the agent

DIMENSION OF HEALTH HOST FACTORS OF DISEASE

Genetic make up
1. Physical
2. Mental Age
3. Emotional Sex
Race
4. Social
5. Spiritual Habits, customs, and tradition
6. Sexual Exposure to the agent
Defense mechanism of the host
CONCEPT OF HEALTH AND DISEASE State of nutrition

3. Environment
Disease
a diagnostic category which classifies a particular illness, sum of the organism's external surrounding conditions and
symptoms, or pathological components of the illness influences that affect its life and development.

Illness THREE CATEGORIES:

a highly personal stage wherein he fills unwell, person's
1) Physical
experience of his disease
humidity, weather, topographic features
Normal Health
2) Biologic
state of well-being in which the individual is free from
disabling effect and has sufficient vigor to carry on the usual presence of living agent
requirements of life, with social adaptation that produces
3) Socioeconomic
self-gratification and enjoyment
a range rather than a specific entity population density, priority is food not health, lack of
awareness, presence of fast food, urbanization, political
commitment
Holistic Health
views a person being whose psycho-socialcultural-spiritual-
relationships with the environment directly affect health Biological laws for Communicable and Non-Communicable
Disease
DETERMINANTS OF HEALTH AND DISEASE
disease results from an imbalance between a disease agent
1. Genes and man
nature and extent of the imbalance depends on the nature
2. Nutrition and characteristics of the host and the agent
essential causes of malnutrition the characteristics of the two are influenced considerably by
a. Failure to ingest food poverty the conditions of the environment.
b. Failure to utilize food PKU, celiac disease, pernicious
anemia

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 ECOLOGIC MODELS OF DISEASE CAUSATION POSSIBLE RESULTS OF INFECTION

Epidemiologic Triangle Recovery

a change in one of the components causes change in the host can ward off infection or disease agent
other
HOST Balanced equilibrium
forces of agent and host are equal so both are not affected;
dangerous because host becomes a healthy carrier (in
apparent infection)
AGENT ENVIRONMENT
Subclinical conditions
Web of Causation very mild reaction that escape
Disease never depends on a single isolated cause but rather
develops as a result of chains of causation Clinical case
full-blown case which way either be atypical or typical
Wheel
depicts the relationship of host with its genetic material and REQUIREMENTS FOR INFECTION TO OCCUR
how it is influenced by the environment
1. Presence of agent
2. Suitable reservoir

INCUBATION PERIOD
interval between the time of entry of agent into the host and
the onset of signs and symptoms
time required for the agent to establish itself to multiply or
secrete toxins.

This varies based on the following condition:

Virulence, dose, and portal of entry

NATURAL HISTORY OF DISEASE Previous experience of the host
State of natural resistance
comprises the body of both qualitative and quantitative The inherent character of the organism
knowledge of agent, host and environmental factors and
its development from the first forces which initiate the 3. Presence of susceptible host
process in the environment through the resulting changes
that take place in man and continuing until equilibrium is Clinical Horizon
reached, or defect, disability or death ensues. Clinical manifestation of disease which appear after the
incubation period
TWO PHASES OF THE NATURAL HISTORY OF DISEASE E.g., Fever- most common symptom: Continuous (dengue)
Intermittent (malaria) - up and down fever but the
1. Pre-pathogenesis (state of susceptibility) temperature reaches normal range
phase before man is involved Remittent (typhoid) up and down fever but
preliminary interaction of host, agent, and environmental
factors in disease production
4. Suitable portal of entry

PORTAL OF ENTRY
A suitable portal of entry is requisite for a successful
infection.
The portal of entry may also be the portal of exit.
Possible portals of entry:
Respiratory tract
Mucous membranes
Skin and subcutaneous tissue
GIT
Conjunctiva
Placenta
2. Pathogenesis (stage of disability) GUT
course of the disease in man from the first interaction with
the disease, provoking stimuli to the changes in the form and 5. Portal exit from the host
function which results until equilibrium is reached or 6. Appropriate means of dissemination
recovery, defect, disability, or death ensues
changes cause the signs and symptoms ---> diagnosis is Period of Communicability
needed
period at which the patient is very infectious
may be short in certain diseases such as SVI or very long for
disease with a carrier state (serves as reservoir of infection
in man), like in typhoid.

TYPES OF CARRIERS:

1. Incubatory
having an elapsed time between first exposure to pathogen
and first appearance of symptoms (measles)

2. Convalescence
despite disappearance of symptoms, the patient still contains
the organism (cholera, diphtheria)

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3. Temporary Avoidance of various carcinogenic agents and
patient is infectious only during the period of illness treatment of pre-cancerous lesions
(influenza) Protection against occupational hazards.
4. Chronic Protection from accidents
patient continuously sheds off the infectious for a long period Controls of aspects of human behavior such as dietary
of time (typhoid, HIV, HBV, TB) habits, tobacco, drugs, and alcohol abuse.

Characteristics of the agents directly related to the host: B. SECONDARY PROTECTION

1. Antigenicity Measures applied during early pathogenesis

ability to induce antibody production Early diagnosis and Prompt treatment
Applies during subclinical (pre-symptomatic) or early clinical
2. Toxicity phase of the disease
ability to produce toxin
Objectives:
3. Invasiveness
ability to penetrate or grow within the host away from the 1. Prevent spread of infection if disease is infectious.
original site of illness (Eliminate agent and reservoir)

4. Virulence 2. To cure or arrest the disease process in order to prevent

ability to cause serious illness complication

5. Pathogenicity 3. To prevent prolonged disability

ability to cause disease Ex: Case finding in PTB, cancer screening

6. Infectivity C. TERTIARY PREVENTION

ability to lodge in the host and multiply in the body of the host
Applies to advanced stage of pathogenesis
III. LEVELS OF PREVENTION To return the individual to a useful place in society and make
maximum use of his remaining capacities.
PREVENTION Examples: DISABILITY LIMITATION, REHABILITATION,
is inhibiting the development of the disease before it occurs INTENSIVE FOLLOW-UP, AND TREATMENT OF CASES
and other measures which will interrupt or slow down the
progression of the disease once it occurs. IV.DEMOGRAPHY

A. PRIMARY PREVENTION Science of Population

Focuses its attention to three human phenomena:
prevention of the disease by altering the susceptibility and Population size
reducing risks for susceptible individuals. Composition of the population
These are the measures which can be accomplished during Distribution of the population in space
the pre-pathogenesis stage.
TOOLS FOR DEMOGRAPHY
GENERAL HEALTH PROMOTION (Primordial Prevention)
1. Counts
measures employed in promoting health, not directed to any absolute numbers of a population or any demographic event
disease but serve to further the general health and well being occurring in a specified area during a specified time period.
Health education and motivation are important in this period. Examples:
(To increase awareness and the knowledge of people on 30,443,287 males in the Phil. in 1990
how to improve health) 77,322 live births in Manila in 1984

Examples: 2. Ratio
Good standard of nutrition. single number that represents the relative size of two
Counseling and parent education numbers
Development of good habits of health and hygiene Relation of one population subgroup to another subgroup in
Prompt utilization of available health facilities the same population It takes the form of:
Adequate housing and recreation. When K = 100, the proportion becomes a percentage.
No overcrowding, adequate ventilation Example:
Cleanliness of the surrounding 100 number of males sex ratio x number of females
Sports activities
Sex education and counseling before and during 3. Proportion
marriage special type of ratio in which the numerator is part of the
Genetics denominator o Relation of a population subgroup to the
entire population
SPECIFIC PROTECTION It takes the form:
When K = 100, the proportion becomes a percentage.
Use of measures against specific disease agents by
establishing barriers against agents in the environment 4. Rate
frequency of occurrence of events over a given interval of
Altering susceptibility and reducing exposure (risk reduction)
Use of measures against specific disease agents by time
establishing barrier against agents in the environment Most rates are expressed per 1000 population
Crude Rate computed for an entire population
Examples: Examples: Crude Death Rate (CDR), Crude Birth Rate
Isolation and quarantine - isolate the cases, quarantine (CBR)
*Specific Rate computed for a specific subgroup (e.g.,
the exposed.
Control means of spread General Fertility Rate)
Spread of the disease through direct/indirect contact,
vector, vehicle, fomite.
Proper waste disposal
Food, water, and milk sanitation
Immunization increases resistance of host
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 V. MEASURES OF CENTRAL TENDENCY AND DISPERSION 2. Specificity
ability of the test to identify correctly those who do
A. MEASURES OF CENTRAL TENDENCY not have the disease

1. Mean COMPARISON OF RESULT OF A DICHOTOMOUS TEST WITH

The sum of the scores or values of a variable divided by their ACTUAL DISEASE STATUS
number
Disease Status
Test Result
With Disease Without Disease
True Positive (TP) False Positive (FP)
(+) Have disease and have No disease but have (+) test
2. Median (+) test result result
The value of the middle item when the items are arranged False Negative (FN) True Negative (TN)
according to magnitude (-) Have disease but (-) test No disease and have (-) test
Middlemost observation in a set of observations arranged in result result
numerical order or in an array
If n is odd, it is the middlemost observation
If n is even, it is the mean of the two middlemost
observations
Arrange the observations according to magnitude (array) and
use the corresponding formula

3. Mode
The score of the values which occurs with the greatest
frequency

Location of the measures of central tendency:

Symmetrical Distribution
Skewed to the Left
Skewed to the Right

B. MEASURES OF DISPERSION

1. Range
2. Variance
3. Standard deviation
4. Coefficient of variation

VI. STUDY DESIGN

1. Observational
observe things happen

a. Descriptive - occurrence and distribution of diseases

b. Analytic - test for hypothesis

2. Experimental
there is intervention

a. True experiment - with randomization

b. Quasi-experiment - without randomization

TYPES OF DESCRIPTIVE STUDY DESIGN

Descriptive Case Report
Case Series
Ecologic
Analytic Case Control
Cohort
Both Descriptive & Analytic Cross Sectional

VII. VALIDITY OF TEST

The ability of the test to distinguish between who has the

Measured by its ability to do what it is supposed to do

Components:

1. Sensitivity
ability of the test to identify correctly those who
have the disease

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