GENERAL MEDICINE

KMTC MERU CAMPUS

ORTHOPEDIC AND TRAUMA MEDICINE
MR. FREDDY BUNDI
 Communicable diseases

Communicable disease defination

 A disease that is transmitted through direct contact with an infected individual or
indirectly through a vector:contagious disease
 The term disease refers to a disturbance in the normal functioning of the body and is
used interchangeably with ‘illness’. Diseases may be classified as communicable or non-
communicable.
 The organisms that cause communicable diseases are called infectious agents, and
their transmission to new uninfected people is what causes communicable diseases; (note
that infectious diseases is an interchangeable term).
 Familiar examples of communicable diseases are malaria and tuberculosis.
Factors involved in the transmission of communicable diseases
 Transmission is a process in which several events happen one after the other in the form
of a chain.
 Hence, this process is known as a chain of transmission .
Six major factors can be identified:
 the infectious agent
 the reservoir
 the route of exit
 the mode of transmission
 the route of entry and
 the susceptible host.
 Infectious agents can have varying sizes. Some, such as Plasmodium
falciparum and all bacteria and viruses, are tiny and are called micro-
organisms, because they can only be seen with the aid of microscopes.
 Others, such as the ascaris worm (Ascaris lumbricoides), can be easily seen
with the naked eye.
Reservoir
 The place where the infectious agent is normally present before infecting a new
human is called a reservoir.
 Without reservoirs, infectious agents could not survive and hence could not be
transmitted to other people.
 Humans and animals which serve as reservoirs for infectious agents are known
as infected hosts.
 Two examples are people infected with HIV and with the bacteria that cause
tuberculosis; these infectious agents persist and multiply in the infected hosts
and can be directly transmitted to new hosts.
 Animals can also be reservoirs for the infectious agents of some communicable
diseases.

 For example, dogs are a reservoir for the virus that causes rabies.
 Diseases such as rabies, where the infectious agents can be transmitted from
animal hosts to susceptible humans, are called zoonoses (singular, zoonosis).
 Non-living things like water, food and soil can also be reservoirs for infectious
agents, but they are called vehicles (not infected hosts) because they are not
alive.
Route of exit
 Before an infectious agent can be transmitted to other people, it must first get
out of the infected host.
 The site on the infected host through which the infectious agent gets out is
called the route of exit e.g respiratory tract
Mode of transmission
 Once an infectious agent leaves a reservoir, it must get transmitted to a new
host if it is to multiply and cause disease. The route by which an infectious
agent is transmitted from a reservoir to another host is called the mode of
transmission.
 Direct transmission refers to the transfer of an infectious agent from an
infected host to a new host, without the need for intermediates such as air,
food, water or other animals. Direct modes of transmission can occur in two
main ways:
 Person to person: The infectious agent is spread by direct contact
between people through touching, biting, kissing, sexual intercourse or
direct projection of respiratory droplets into another person’s nose or
mouth during coughing, sneezing or talking. A familiar example is the
transmission of HIV from an infected person to others through sexual
intercourse.
 Transplacental transmission: This refers to the transmission of an
infectious agent from a pregnant woman to her fetus through the placenta.
An example is mother-to-child transmission (MTCT) of HIV.
Indirect modes of transmission
 Indirect transmission is when infectious agents are transmitted to new
hosts through intermediates such as air, food, water, objects or substances in
the environment, or other animals. Indirect transmission has three subtypes:
 Airborne transmission: The infectious agent may be transmitted in dried
secretions from the respiratory tract, which can remain suspended in the air for
some time. For example, the infectious agent causing tuberculosis can enter a
new host through airborne transmission.
 Vehicle-borne transmission: A vehicle is any non-living substance or
object that can be contaminated by an infectious agent, which then transmits it
to a new host. Contamination refers to the presence of an infectious agent in
or on the vehicle.
 Vector-borne transmission: A vector is an organism, usually an
arthropod, which transmits an infectious agent to a new host. Arthropods
which act as vectors include houseflies, mosquitoes, lice and ticks.
Route of entry
 Successful transmission of the infectious agent requires it to enter the host
through a specific part of the body before it can cause disease. The site through
which an infectious agent enters the host is called the route of entry.
Susceptible host
 After an infectious agent gets inside the body it has to multiply in order to
cause the disease. In some hosts, infection leads to the disease developing,
but in others it does not. Individuals who are likely to develop a
communicable disease after exposure to the infectious agents are called
susceptible hosts. Different individuals are not equally susceptible to
infection, for a variety of reasons.
 Factors that increase the susceptibility of a host to the development of a
communicable disease are called risk factors.
 Some risk factors arise from outside the individual – for example, poor
personal hygiene, or poor control of reservoirs of infection in the environment.
 Factors such as these increase the exposure of susceptible hosts to infectious
agents, which makes the disease more likely to develop.
 Additionally, some people in a community are more likely to develop the
disease than others, even though they all have the same exposure to
infectious agents.
 This is due to a low level of immunity within the more susceptible
individuals.
 Immunity refers to the resistance of an individual to communicable
diseases, because their white blood cells and antibodies (defensive
proteins) are able to fight the infectious agents successfully.
Low levels of immunity could be due to:
 diseases like HIV/AIDS which suppress immunity
 poorly developed or immature immunity, as in very young children
 not being vaccinated
 poor nutritional status (e.g. malnourished children)
 pregnancy.
Natural history of a communicable disease
 The natural history of a disease is also referred to as the course of the disease,
or its development and progression; these terms can be used interchangeably.
Events that occur in the natural history of a communicable disease are
grouped into four stages: exposure, infection, infectious disease, and
outcome. We will briefly discuss each of them in turn.
Stage of exposure
 Here a contact refers to an association between a susceptible host and a
reservoir of infection, which creates an opportunity for the infectious agents to
enter the host.
 In the stage of exposure, the susceptible host has come into close contact
with the infectious agent, but it has not yet entered the host’s body cells.
Examples of an exposed host include:
 a person who shakes hands with someone suffering from a common cold
 a child living in the same room as an adult with tuberculosis
 a person eating contaminated food or drinking contaminated water.
Stage of infection
 At this stage the infectious agent has entered the host’s body and has begun
multiplying. The entry and multiplication of an infectious agent inside the host
is known as the stage of infection. For instance, a person who has eaten food
contaminated with Salmonella typhii (the bacteria that cause typhoid fever) is
said to be exposed; if the bacteria enter the cells lining the intestines and start
multiplying, the person is said to be infected.
 At this stage there are no clinical manifestations of the disease, a term
referring to the typical symptoms and signs of that illness. Symptoms are the
complaints the patient can tell you about (e.g. headache, vomiting, dizziness).
Signs are the features that would only be detected by a trained health worker
(e.g. high temperature, fast pulse rate, enlargement of organs in the abdomen).
Stage of infectious disease
 At this stage the clinical manifestations of the disease are present in the
infected host. For example, a person infected with Plasmodium falciparum,
who has fever, vomiting and headache, is in the stage of infectious disease
– in this case, malaria. The time interval between the onset (start) of infection
and the first appearance of clinical manifestations of a disease is called the
incubation period. For malaria caused by Plasmodium falciparum the
incubation period ranges from 7 to 14 days.
 Remember that not all infected hosts may develop the disease, and among
those who do, the severity of the illness may differ, depending on the level of
immunity of the host and the type of infectious agent. Infected hosts who have
clinical manifestations of the disease are called active cases. Individuals who
are infected, but who do not have clinical manifestations, are called carriers.
Carriers and active cases can both transmit the infection to others.
 Depending on the time course of a disease and how long the clinical manifestations persist,
communicable diseases can be classified as acute or chronic.
 Acute diseases are characterised by rapid onset and short duration of illness. For instance,
diarrhoea that starts suddenly and lasts less than 14 days is an acute diarrhoeal disease.

 Chronic diseases are characterised by prolonged duration of illness; for example, a chronic
diarrhoeal disease lasts more than 14 days.
Stage of outcome
 At this stage the disease may result in recovery, disability or death of the
patient. For example, a child who fully recovers from a diarrhoeal disease, or is
paralyzed from poliomyelitis, or dies from malaria, is in the stage of outcome
 Introduction to infections

 An infection is the invasion of an organism's body tissues by

disease-causing agents, their multiplication, and the reaction of host tissues to
the infectious agents and the toxins they produce. An infectious disease, also
known as a transmissible disease or communicable disease, is an illness
resulting from an infection.
An infection happens when a foreign organism enters a person's body and causes
harm.The organism uses that person's body to sustain itself, reproduce, and
colonize. These infectious organisms are known as pathogens. Examples of
pathogens include bacteria, viruses, fungi, and prions. Pathogens can
multiply and adapt quickly.
 Types of infections

 Bacteria
 viruses
 fungi
 protozoa,
 parasites, and
 prions are different types of pathogen. They vary in their size, shape, function,
genetic content, and how they act on the body.
Viral infections
 The common cold is a viral infection.
 Viral infections are caused by a virus.
 Millions of types of virus are thought to exist, but only 5,000 types have been
identified.
 Viruses contain a small piece of genetic code.
 They are protected by a coat of protein and fat.
 Viruses invade a host and attach themselves to a cell.
 As they enter the cell, they release genetic material.
 The genetic material forces the cell to replicate, and the virus multiplies.
 When the cell dies, it releases new viruses, and these go on to infect new cells.
 Not all viruses destroy their host cell.
 Some of them change the function of the cell.
 In this way, viruses such as human papillomavirus (HPV) or Epstein-Barr virus
(EBV) can lead to cancer by forcing cells to replicate in an uncontrolled way.
 They can also target certain age groups, such as infants or young children.
 A virus may remain dormant for a period before multiplying again.
 The person with the virus can appear to have recovered but may get sick again
when the virus reactivates.
Here are some examples of viral infections:
 the common cold, mainly caused by the rhinovirus, coronavirus, and adenovirus
 encephalitis and meningitis, caused by enteroviruses and the herpes viruses
 warts and skin infections, caused by the human papillomaviruses (HPV) and herpes
simplex virus (HSV).
 gastroenteritis, caused by the novavirus
Other viral conditions include:
 Zika virus
 human immunodeficiency virus (HIV)
 hepatitis C
 polio
 influenza
 Dengue fever
 H1N1 swine flu
 Ebola
 Middle East respiratory syndrome (MERS-CoV)
 Antiviral medications help in some cases.
 They can either prevent the virus from reproducing or boost the host's immune
system.
 Antibiotics are not effective against viruses.
 Using antibiotics against a virus will not stop the virus, and it increases the risk
of antibiotic resistance.
 Examples of viral infections

Varicella zoster virus (VZV) infection

 VZV produces two distinct diseases, varicella (chickenpox) and herpes zoster
(shingles).
 The primary infection is chickenpox. It usually occurs in childhood, the virus
entering through the mucosa of the upper respiratory tract.
 It should be noted that in some countries (e.g. the Indian subcontinent) a
different epidemiological pattern exists with most infections occurring in
adulthood.
 Chickenpox rarely occurs twice in the same individual.
 Infectious virus is spread from fresh skin lesions by direct contact or airborne
transmission and the period of infectivity in chickenpox extends from 2 days
before the appearance of the rash until the skin lesions are all at the crusting
stage.
 Following recovery from chickenpox the virus then remains latent in dorsal
root and cranial nerve ganglia.
Clinical features of chickenpox
 Fourteen to twenty-one days after exposure to VZV, a brief prodromal illness of
fever, headache and malaise heralds the eruption of chickenpox, characterized
by the rapid progression of macules to papules to vesicles to pustules in a
matter of hours. In young children the prodromal illness may be very mild or
absent.
 The illness tends to be more severe in older children and can be debilitating in
adults.
 The lesions occur on the face, scalp and trunk, and to a lesser extent on the
extremities.
 It is characteristic to see skin lesions at all stages of development on the same
area of skin.
 Fever subsides as soon as new lesions cease to appear. Eventually the pustules
crust and heal without scarring.
 Important complications of chickenpox include pneumonia, which
generally begins 1-6 days after the skin eruption, and bacterial superinfection of
skin lesions.
 Pneumonia is more common in adults than in children and cigarette smokers
are at particular risk.
Mumps
 Mumps is the result of infection with a paramyxovirus. It is spread by droplet
infection, by direct contact or through fomites. Humans are the only known
natural hosts.
 The peak period of infectivity is 2-3 days before the onset of the parotitis and
for 3 days afterwards.
 Clinical features The incubation period averages 18 days. Although no age is
exempt, it is primarily a disease of school-aged children and young adults; it is
uncommon before the age of 2 years.
The prodromal symptoms are non-specific and include fever, malaise, headache
and anorexia. This is usually followed by severe pain over the parotid glands, with
either unilateral or bilateral parotid swelling. The enlarged parotid glands obscure
the angle of the mandible and may elevate the ear lobe, which does not occur in
cervical lymph node enlargement. Trismus due to pain is common at this stage.
Submandibular gland involvement occurs less frequently.
Complications
 CNS involvement is the most common extrasalivary-gland manifestation of
mumps.
 Clinical meningitis occurs in 5% of all infected patients, and 30% of patients
with CNS involvement have no evidence of parotid gland involvement.
 Epididymo-orchitis develops in about one-third of patients who develop
mumps after puberty. Bilateral testicular involvement results in sterility in only
a small percentage of these patients.
 Pancreatitis, oophoritis, myocarditis, mastitis, hepatitis and polyarthritis may
also occur.
 Diagnosis and treatment
 The diagnosis of mumps is on the basis of the clinical features. In doubtful
cases, serological demonstration of a fourfold rise in antibodies detected by
complement fixation or indirect haemagglutination or neutralization tests on
acute and convalescent sera is diagnostic. Virus can be isolated in cell culture
from saliva, throat swab, urine and CSF and identified by immunofluorescence
or haemadsorption.
 CORONAVIRUSES
 Human coronaviruses were first isolated in the mid 1960s and the majority of
isolates (related to the reference strains 229E and OC43) have been associated
with common colds.
 In November 2002, an apparently new viral disease occurred in China
(Guangdong province) and this spread rapidly in other parts of the Far East and
also in Canada (Toronto and Vancouver). This disease, known as 'severe acute
respiratory syndrome' (SARS-COV) of which bronchopneumonia has been a
major feature, is caused by a previously unknown coronavirus.
 Similarity of this virus to coronaviruses isolated from civet cats, raccoons and
ferret badgers indicates the likelihood that SARS is a zoonotic disease .
 The epidemic was finally brought under control in the summer of 2003 and by
then there had been > 8000 cases with approximately 800 deaths.
 But in december 2019 an epidemic started in china known as covid-19 is
spread rapidily to many countries causing massive deaths. The epidemic has
claimed thousands of lives and still continuing claiming lives.
Clinical manifestation;incubation period is 3-14 days of getting into contact with
an infected person.The disease is highly contagious.History of travel in a
country with the epidemic and having the following symtoms
Fever
Cold
Sore throat
Difficulty in breathing
Loss of smell sensation
Prevention and treatment
 Observing hygiene-washing hands with antiseptic/sanitiser/soap and water
 Isolating of infected people
 Avoiding crowded places
 Avoiding touching of surfaces
 Use PPE
 Use of protective while coughing or sneezing
Treatment
 Disease is self limiting
 Though can use analgesics,antibiotics,oxygen if needed
 Bacterial infections

 Bacteria are single-celled microorganisms known as prokaryotes.

 There are estimated to be at least one nonillion bacteria on Earth.
 A nonillion is a one followed by 30 zeros.
 Much of Earth's biomass is made up of bacteria.
Bacteria take three main shapes:
 Spherical: These are usually the simplest to treat and are known as cocci.
 Rod-shaped: These are called bacilli.
 Spiral: Coiled bacteria are known as spirilla. If the coil of a spirillus is particularly
tight, they are known as spirochetes.
 Bacteria can live in almost any kind of environment, from extreme heat to intense
cold, and some can even survive in radioactive waste.
 There are trillions of strains of bacteria, and few of these cause diseases in
humans.
 Some of them live inside the human body without causing harm, for example in
the gut or airways. Some "good" bacteria attack "bad" bacteria and prevent them
from causing sickness.
 However, some bacterial diseases are deadly.

These include:
 cholera
 diphtheria
 dysentery
 bubonic plague
 pneumonia
 tuberculosis
 typhoid
 typhus
Some examples of bacterial infections are:
 bacterial meningitis
 otitis media
 pneumonia
 tuberculosis
 upper respiratory tract infection
 gastritis
 food poisoning
 eye infections
 sinusitis
 urinary tract infections
 skin infections
 sexually transmitted diseases
Bacterial infections can be treated with antibiotics, but some strains become
resistant and can survive the treatment
Bacteria Infections of the skin includes; Pyoderma
 Abscesses
 Cellulitis
 Erysypelas
 Ecythyma
 Impetigo
 Folliculitis
 Furuncle(boil)
 carbuncle
Staphylococcal scalded skin syndrome
 The scalded skin syndrome is caused by a toxin-secreting strain of S. aureus.
 It principally affects children under the age of 5.
 The toxin, exfoliatin, causes intra-epidermal cleavage at the level of the
stratum corneum leading to the formation of large flaccid blisters that shear
readily.
 It is a relatively benign condition, and responds to treatment with flucloxacillin.
Gas gangrene
 Gas gangrene is caused by deep tissue infection with Clostridium spp.,
especially C. perfringens, and follows contaminated penetrating injuries.
 It is particularly associated with battlefield wounds, but is also seen in
intravenous drug users, and following surgery.
 The initial infection develops in an area of necrotic tissue caused by the original injury;
toxins secreted by the bacteria kill surrounding tissue and enable the anaerobic
organism to spread rapidly.
 Toxins are also responsible for the severe systemic features of gas gangrene.
 Treatment consists of urgent surgical removal of necrotic tissue, and treatment with
benzylpenicillin and clindamycin.
Pertussis (whooping cough)
 Pertussis occurs world-wide.
 Humans are both the natural hosts and reservoirs of infection.
 The disease is caused by Bordetella pertussis which is a Gram-negative coccobacillus.
B. parapertussis and B. bronchiseptica produce milder infections.
 Pertussis is highly contagious and is spread by droplet infection.
 In its early stages it is indistinguishable from other types of upper respiratory tract
infection.
 Epidemic disease occurred in the UK when the safety of the whooping cough vaccine
was questioned.
 Currently, uptake exceeds 95% and the disease is uncommon.
Clinical features
 The incubation period is 7-10 days.
 It is a disease of childhood, with 90% of cases occurring below 5 years of age.
 However, no age is exempt.
 During the catarrhal stage the patient is highly infectious, and cultures from
respiratory secretions are positive in over 90% of patients.
 Malaise, anorexia, mucoid rhinorrhoea and conjunctivitis are present.
Diagnosis
 The diagnosis is suggested clinically by the characteristic whoop and a history of
contact with an infected individual.
 It is confirmed by isolation of the organism. Cultures of swabs of nasopharyngeal
secretions result in a higher positive yield than cultures of 'cough plates'.
Treatment
 If the disease is recognized in the catarrhal stage, erythromycin will abort or
decrease the severity of the infection. In the paroxysmal stage, antibiotics have little
role to play in altering the course of the illness.
 Prevention and control
 Affected individuals should be isolated to prevent contact with others, e.g.
in hostels and boarding schools.
 Pertussis is an easily preventable disease and effective active immunization
is available .
 Convulsions and encephalopathy have been reported as rare complications
of vaccination but they are probably less frequent than after whooping
cough itself.
 Any exposed susceptible infant should receive prophylactic erythromycin.
Vibrio Cholera,
due to Vibrio cholerae is the prototypic pure enterotoxigenic diarrhoea: Vibrio
parahaemolyticus causes acute watery diarrhoea after eating raw fish or
shellfish that has been kept for several hours without refrigeration.
 Explosive diarrhoea, abdominal cramps and vomiting occurs with a fever in
50%. It is self-limiting, lasting up to 10 days.
Bacillus cereus
 B. cereus produces two toxins.
 One produces watery diarrhoea up to 12 hours after ingesting the organism.
 The other toxin is preformed in food and causes severe vomiting, e.g. 'fried rice
poisoning'
Travellers' diarrhoea
 Travellers' diarrhoea is defined as the passage of three or more unformed
stools per day in a resident of an industrialized country travelling in a
developing nation.
 Infection is usually food- or water-borne, and younger travellers are most often
affected (probably reflecting behaviour patterns). Reported attack rates vary
from country to country, but approach 50% for a 2-week stay in many tropical
countries.
 The disease is usually benign and self-limiting:
 treatment with quinolone antibiotics may hasten recovery but is not normally
necessary.
 Prophylactic antibiotic therapy may also be effective for short stays, but should
not be used routinely.
 Common causes of travellers' diarrhoea (TD) Organism Frequency
(varies from country to country)
 ETEC ( enterotoxigenic Escherichia coli) 30-70%
 Shigella spp. 0-15%
 Salmonella spp. 0-10%
 Campylobacter spp. 0-15%
 Viral pathogens 0-10%
 Giardia intestinalis 0-3%
 Fungal infections

 Fungi reproduce by spreading spores.

 A fungus is an often multi-cellular parasite that can decompose and
then absorb organic matter using an enzyme.
 They almost always reproduce through the spreading of single-celled
spores, and the structure of a fungus is normally long and cylindrical
with small filaments branching from the main body.
 This structure is known as hypha.
 There are approximately 51 million species of fungus.
 Many fungal infections will appear in the upper layers of the skin,
and some progress to the deeper layers.
 Inhaled fungal spores can lead to systemic fungal infections, such as
thrush, or candidiasis.
 Systemic diseases affect the whole body.
 Examples of fungal infections are:
 valley fever, or coccidioidomycosis
 athlete's foot
 ringworm
 some eye infections
 A rash can be an indicator of a fungal infection of the skin.
 Candidiasis: Candidiasis is the most common fungal infection in humans and
is predominantly caused by Candida albicans although other species of
Candida are increasingly recognized.
 Candida are small asexual fungi. Most species that are pathogenic to humans
are normal oropharyngeal and gastrointestinal commensals. Candidiasis is
found world-wide.
Clinical features
 Any organ in the body can be invaded by candida, but vaginal infection and oral
thrush are the most common forms.
 This latter is seen in the very young, in the elderly, following antibiotic therapy
and in those who are immunosuppressed.
 Candidal oesophagitis presents with painful dysphagia. Cutaneous candidiasis
typically occurs in intertriginous areas. It is also a cause of paronychia.
 Balanitis and vaginal infection are also common
Pneumocystis carinii
 infection Genetic analysis has shown this organism to be homologous with
fungi.
 It exists as a trophozoite which is probably motile and reproduces by binary
fission. After invasion the trophozoite wall thickens and forms a cyst.
 On maturation further division takes place to yield eight merozoites which after
cell wall rupture develop into trophozoites.
Infection probably occurs in infancy but in otherwise healthy infants it remains
undetected. It is usually cleared from the lungs. P. carinii disease in adults is
associated with immunodeficiency states, particularly AIDS.
 Dermatophytosis: Dermatophytoses are chronic fungal infections of
keratinous structures such as the skin, hair or nails. Trichophyton spp.,
Microsporum spp., Epidermophyton spp. and Candida spp. can also infect
keratinous structures.
 Malassezia infection
 Malassezia spp. are found on the scalp and greasy skin and are responsible for
seborrhoeic dermatitis, pityriasis versicolor (hypo- or hyperpigmented rash on
trunk) and Malassezia folliculitis (itchy rash on back).
 Treatment is with topical antifungals or oral ketoconazole if infection is
extensive.
 Prion disease/infection

 A prion is a protein that contains no genetic material. It is normally harmless,

but if it folds into an abnormal shape, it can become a rogue agent and affect
the structure of the brain or other parts of the nervous system.
 Prions do not replicate or feed on the host but trigger abnormal behavior in the
body's cells and proteins.
 Prion diseases are rare, but they progress rapidly, and all are currently fatal.
Prions cause degenerative brain diseases, such as:
 bovine spongiform encephalopathy (BSE), also known as mad cow disease
 Creutzfeldt-Jakob disease (CJD)
 Researchers have linked some cases of Alzheimer's disease to prion infection.
 Other infections

 While the forms of infection mentioned above are the main types, there are
others that can have an effect on the body.
 A single-celled organism with a nucleus can cause a protozoan infection.
 Protozoa commonly show features similar to animals, such as mobility, and
can survive outside of the human body.
 They are most commonly transferred by contact with feces.
 When they enter the human body, protozoa can also cause infection.
 Amebic dysentery is an example of a protozoan infection.
 Helminths are larger, multicellular organisms that tend to be visible to the
naked eye when full-grown.
 This type of parasite includes flatworms and roundworms.
 These are also able to infect the human body
 Finally, ectoparasites such as mites, ticks, lice, and fleas can cause infection
by attaching or burrowing into the skin.
 The term can also include blood-sucking arthropods, such as mosquitos, that
transmit infection by consuming human blood.
CAUSE.
 The cause of an infection is said to be whichever type of organism has invaded
the body.
 A particular virus, for example, will be the cause of a viral infection.
 The effects of an infection, such as swelling or a runny nose, occur as a result of
the immune system fighting the invading organism.
 A wound filling with pus, for example, occurs when white blood cells rush to
the site of an injury to combat foreign bacteria.
SYMPTOMS
 The symptoms of an infection depend on the organism responsible as well as
the site of the infection.
 Viruses target specific cells, such as those in the genitals or upper respiratory
tract.
 The rabies virus, for example, targets the nervous system.
 Some viruses target skin cells, causing warts.
 Others target a wider range of cells, leading to various symptoms.
 A flu virus can cause a runny nose, muscle aches, and an upset stomach.
 A person with a bacterial infection will often experience redness and heat,
swelling, fever, pain at the site of infection, and swollen lymph glands.
 Prevention

 There is no single way to prevent all infectious diseases, but the following tips
can reduce the risk of transmission:
 Wash your hands often, especially before and after preparing food and after
using the bathroom.
 Clean surface areas and avoid leaving room-temperature food exposed when
cooking.
 Receive any recommended vaccinations, and keep them up to date.
 Only take antibiotics when prescribed, and be sure to complete any
recommended course even if symptoms improve earlier than anticipated.
 Disinfect rooms where there may be high concentrations of bacteria, such as
the kitchen and bathroom.
 Practice safe sex by receiving regular STD checks, using condoms, or abstaining
altogether.
 Avoid sharing personal items such a toothbrushes, combs, razorblades,
drinking glasses, and kitchen utensils.
 Acute and chronic diseases

What is acute Disease?

 A few diseases occur suddenly and last for a few days.
 These are known as acute diseases, such as common cold.
 This condition can be treated with medical treatment or on its own. Many times,
acute diseases turn chronic if they continue to persist.
 Acute diseases can occur throughout all body systems.
 For eg, the first asthma attack is acute which later turns chronic. Strep throat,
broken bone, appendicitis, influenza, pneumonia, etc. are some of the acute
diseases.
What is a Chronic Disease?
 The diseases that occur over a period of time and last longer, or even for the
lifetime are called chronic diseases.
 Generally, if a disease lasts for more than three years it is called a chronic disease.
 Initially, the symptoms are very mild. A chronic disease progresses slowly and
damages the body severely.
 It might sometimes be fatal.
 The risk factors involved in such diseases may be age, gender, an unhealthy
lifestyle, etc.
 A chronic disease may or may not be cured by medications.
 It cannot be prevented by vaccines as well.
 Elephantiasis, Hepatitis C, HIV, arthritis, diabetes mellitus are some of the
chronic diseases.
However, chronic disease can be controlled by:
 participation in physical activity
 healthy diet
 no smoking
 controlling alcohol consumption
 A chronic illness is very stressful. The stress obstructs and delays your recovery.
Differences between Acute and Chronic Diseases
 Acute Diseases Chronic Diseases
 occur suddenly. occur over a prolonged period.
 last shorter period. They last longer
 Key Points on Acute and Chronic Diseases
 Acute diseases refer to the medical condition that occurs suddenly and lasts for
a shorter period of time.
 Chronic diseases develop slowly and last for a lifetime.
 Chronic diseases are sometimes fatal.
 Acute diseases when persist for a longer time can term fatal, otherwise can be
treated by certain medications.
 Common cold, typhoid, jaundice, cholera, burn, are some of the acute diseases.
 Chronic diseases include AIDS, elephantiasis, cancer, tuberculosis etc.
 Tropical diseases

Defination
 Tropical diseases encompass all diseases that occur solely, or principally, in the
tropics. In practice, the term is often taken to refer to infectious diseases that thrive
in hot, humid conditions, such as malaria, leishmaniasis, schistosomiasis,
onchocerciasis, lymphatic filariasis, Chagas disease, African trypanosomiasis, and
dengue.
COMMON EXAPMLES.
 Chagas disease (also called American trypanosomiasis) is a parasitic disease which
occurs in the Americas, particularly in South America. Its pathogenic agent is a
flagellate protozoan named Trypanosoma cruzi, which is transmitted mostly by
blood-sucking assassin bugs, however other methods of transmission are
possible, such as ingestion of food contaminated with parasites, blood transfusion
and fetal transmission. Between 16 and 18 million people are currently infected.
 Dengue Helminths African trypanosomiasis or sleeping sickness, is a parasitic
disease, caused by protozoa called trypansomes. The two responsible for African
trypanosomiasis are Trypanosoma brucei gambiense and Trypanosoma brucei
rhodesiense. These parasites are transmitted by the tsetse fly.
 Leishmaniasis

 Leishmaniasis is a disease caused by parasites of the Leishmania type.It is

spread by the bite of certain types of sandflies.
 The disease can present in three main ways: cutaneous, mucocutaneous, or
visceral.
 The cutaneous form presents with skin ulcers, while the mucocutaneous form
presents with ulcers of the skin, mouth, and nose, and the visceral form starts
with skin ulcers and then later presents with fever, low red blood cells, and
enlarged spleen and liver.
 Infections in humans are caused by more than 20 species of Leishmania.
 Risk factors include poverty, malnutrition, deforestation, and urbanization.
 All three types can be diagnosed by seeing the parasites under the microscope.
 Additionally, visceral disease can be diagnosed by blood tests.
 Leishmaniasis can be partly prevented by sleeping under nets treated with
insecticide.
 Other measures include spraying insecticides to kill sandflies and treating
people with the disease early to prevent further spread.
 The treatment needed is determined by where the disease is acquired, the
species of Leishmania, and the type of infection.
Some possible medications used for visceral disease include
liposomal amphotericin B, a combination of pentavalent antimonials and
paromomycin, and miltefosine. For cutaneous disease, paromomycin, fluconazole,
or pentamidine may be effective
Leishmaniasis.
 Malaria

 Malaria is a mosquito-borne infectious disease that affects humans and other

animals.
 Malaria causes symptoms that typically include fever, tiredness, vomiting, and
headaches. In severe cases it can cause yellow skin, seizures, coma, or death.
 Symptoms usually begin ten to fifteen days after being bitten by an infected
mosquito.
 If not properly treated, people may have recurrences of the disease months later.
 In those who have recently survived an infection, reinfection usually causes milder
symptoms.This partial resistance disappears over months to years if the person
has no continuing exposure to malaria.
 Malaria is caused by single-celled microorganisms of the Plasmodium group.
 The disease is most commonly spread by an infected female Anopheles mosquito.
 The mosquito bite introduces the parasites from the mosquito's saliva into a
person's blood.
 The parasites travel to the liver where they mature and reproduce.
 Five species of Plasmodium can infect and be spread by humans.
 Most deaths are caused by P. falciparum because P. vivax, P. ovale, and P.
malariae generally cause a milder form of malaria. The species P. knowlesi
rarely causes disease in humans.
 Malaria is typically diagnosed by the microscopic examination of blood using
blood films, or with antigen-based rapid diagnostic tests.
 Methods that use the polymerase chain reaction to detect the parasite's DNA
have been developed, but are not widely used in areas where malaria is
common due to their cost and complexity.
The risk of disease can be reduced by preventing mosquito bites through the use of
mosquito nets and insect repellents, or with mosquito control measures such as
spraying insecticides and draining standing water.Several medications are
available to prevent malaria in travellers to areas where the disease is common.
Occasional doses of the combination medication sulfadoxine/pyrimethamine are
recommended in infants and after the first trimester of pregnancy in areas with
high rates of malaria.
 Despite a need, no effective vaccine exists, although efforts to develop one are
ongoing.
 The recommended treatment for malaria is a combination of
antimalarial medications that includes an artemisinin.The second medication may be
either mefloquine, lumefantrine, or sulfadoxine/pyrimethamine.
 Quinine along with doxycycline may be used if an artemisinin is not available. It is
recommended that in areas where the disease is commo.

FILARIASIS
 Filariasis is a parasitic disease caused by an infection with roundworms of the
Filarioidea type.[1] These are spread by blood-feeding insects such as black flies and
mosquitoes. They belong to the group of diseases called helminthiases.
 Eight known filarial worms have humans as a definitive hosts. These are divided into
three groups according to the part of the body the effect:
 Lymphatic filariasis is caused by the worms Wuchereria bancrofti, Brugia malayi,
and Brugia timori. These worms occupy the lymphatic system, including the lymph
nodes; in chronic cases, these worms lead to the syndrome of elephantiasis.
 Subcutaneous filariasis is caused by Loa loa (the eye worm), Mansonella streptocerca
, and Onchocerca volvulus. These worms occupy the layer just under the skin. L. loa
causes Loa loa filariasis, while O. volvulus causes river blindness.
 Serous cavity filariasis is caused by the worms Mansonella perstans and Mansonella
ozzardi, which occupy the serous cavity of the abdomen. Dirofilaria immitis, the dog
heartworm, rarely infects humans.
 The adult worms, which usually stay in one tissue, release early larval forms known as
microfilariae into the person's blood. These circulating microfilariae can be taken up
during a blood meal by an insect vector; in the vector, they develop into infective
larvae that can be spread to another person.
 Individuals infected by filarial worms may be described as either "microfilaraemic" or
"amicrofilaraemic", depending on whether microfilariae can be found in their
peripheral blood.
 Filariasis is diagnosed in microfilaraemic cases primarily through direct observation
of microfilariae in the peripheral blood. Occult filariasis is diagnosed in
amicrofilaraemic cases based on clinical observations and, in some cases, by finding a
circulating antigen in the blood.
Signs and symptoms
 The most spectacular symptom of lymphatic filariasis is elephantiasis – edema
with thickening of the skin and underlying tissues—which was the first disease
discovered to be transmitted by mosquito bites. [2] Elephantiasis results when
the parasites lodge in the lymphatic system.
 Elephantiasis affects mainly the lower extremities, while the ears,
mucous membranes, and amputation stumps are affected less frequently.
However, different species of filarial worms tend to affect different parts of the
body; Wuchereria bancrofti can affect the legs, arms, vulva, breasts, and
scrotum (causing hydrocele formation), while Brugia timori rarely affects the
genitals.
 Those who develop the chronic stages of elephantiasis are usually free from
microfilariae (amicrofilaraemic), and often have adverse immunological
reactions to the microfilariae, as well as the adult worms
Cause
 Human filarial nematode worms have complicated life cycles, which primarily consists of
five stages.
 After the male and female worms mate, the female gives birth to live microfilariae by the
thousands.
 The microfilariae are taken up by the vector insect (intermediate host) during a blood meal.
In the intermediate host, the microfilariae molt and develop into third-stage (infective)
larvae.
 Upon taking another blood meal, the vector insect, such as Culex pipiens, injects the
infectious larvae into the dermis layer of the skin. After about one year, the larvae molt
through two more stages, maturing into the adult worms.
 Filariasis is usually diagnosed by identifying microfilariae on Giemsa stained,
thin and thick blood film smears, using the "gold standard" known as the finger
prick test.
 The recommended treatment for people outside the United States is
albendazole combined with ivermectin.
 A combination of diethylcarbamazine and albendazole is also effective.
 schistosomiasis

 Schistosomiasis, also known as snail fever and bilharzia, is a disease

caused by parasitic flatworms called schistosomes.
 The urinary tract or the intestines may be infected.
 Symptoms include abdominal pain, diarrhea, bloody stool, or
blood in the urine.
 Those who have been infected for a long time may experience liver damage,
kidney failure, infertility, or bladder cancer.
 In children, it may cause poor growth and learning difficulty.
 The disease is spread by contact with fresh water contaminated with the
parasites.
 These parasites are released from infected freshwater snails.
 The disease is especially common among children in developing countries, as
they are more likely to play in contaminated water.
 Other high-risk groups include farmers, fishermen, and people using unclean
water during daily living.
 It belongs to the group of helminth infections.
 Diagnosis is by finding eggs of the parasite in a person's urine or stool.
 It can also be confirmed by finding antibodies against the disease in the blood
 Methods to prevent the disease include improving access to clean water and
reducing the number of snails.
 In areas where the disease is common, the medication praziquantel may be
given once a year to the entire group.
 This is done to decrease the number of people infected, and consequently, the
spread of the disease.
 Praziquantel is also the treatment recommended by the
World Health Organization for those who are known to be infected.