1. Human biology
Disease
Microbes are of two types:
• Pathogenic -- can cause disease in human
• Non-pathogenic – does not cause disease in human e.g. E.coli
Types of pathogenic disease in human:
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• Bacterial – e.g. salmonella typhi causes typhoid
2012
• Viral – e.g. HIV causes AIDS
• Fungal – e.g. tinea causes athletes foot
Types of disease:
• Animal vectors
• Air borne –through droplet infection
• Water borne
• Direct contact
• Sexually transmitted
• Food borne
STD [sexually transmitted disease]
• AIDS
• Syphilis
• Gonorrhea
Immunity --- it is the ability of the body to resist infection
• Natural active immunity --- it is a kind of immunity acquired when an individual is able to make its own
antibody against the pathogen. The entry of which is natural.
• Natural passive immunity --- it is a type of immunity acquired where the naturally occurring antibodies
made against the pathogens are taken in form an outside source. The antibodies are not self made
• Artificial passive immunity --- specific antibodies are directly injected into a person acquired form a
different source. Provide immunity temporarily. The antibodies which are injected are called serum
• Vaccine -- A vaccine is an immune biological substance which contains the live or dead form of the pathogen,
which when injected provide lifelong immunity
• Incubation period --- the period between becoming infected by germs and the appearance of the symptoms of
disease
• Vaccination – the process of injecting a person with a harmless [weakened or dead] form of a virus to stimulate
the immune system to produce cells and proteins that will destroy that type of virus
• Carrier – it is an individual which harbours the germs without showing signs and symptoms of the disease and
unknown to discharge the multiplying germs through faeces and expiration.
• Case – it is an individual suffering from a disease and showing signs and symptoms
• Vector – a vector is an individual which is known the causative without itself getting infected.
• Endemic disease – a disease which is always present in an area
• Pendemic disease – a large –scale outbreak of disease which spreads from country to country

2. Human biology
Disease
• Epidemic disease -- a sudden outbreak of disease which spreads quickly through the population of an area
Viral diseases
• What are the diseases caused by viruses?
Influenza Jul. 22
nd
[flu], colds, AIDS, hepatitis, west Nile, measles, herpes, shingles, chicken pox,
monkey pox,2012 small pox, Ebola & some cancers [Epstein barr]
polio,
• Common cold [influenza-‘flu]
Causative agent – influenza virus [affects upper respiratory tract]
The virus changes it s composition very rapidly by mutation. Thus it becomes resistant to medicines or vaccines.
So successful vaccination against common cold is not easy
Mode of transmission ---
By air droplet infection: when a person suffering from common cold sneezes, coughs or even breaths they
spread out a fine spray of pathogens. These pathogens enter into healthy person through the nose during
breathing in and out and thus infect the person
Treatment --- symptomatic treatment
Influenza being a viral disease has got no curative treatment since the virus changes their genetic composition
by mutation very rapidly. So no successful vaccine is available
Prevention ---
• An infected person should cover the mouth while talking, sneezing and coughing with a handkerchief
• Avoid close contact with an infected person
• Do not use personal belongings of an infected person
• Avoid gathering and overcrowded and poorly ventilated places
• Treatment of the infected person helps eliminating the source of infection
• Health education
• Improvement of socio economic condition
• AIDS [acquired immune deficiency syndrome]
Causative agent -- HIV [retrovirus] {human immune deficiency virus} – weakens the immune system
Mode of transmission –
It is transmitted through body fluid by:
• Through sexual intercourse with multiple sexual partners and amongst homosexuals
• Through blood transfusions
• Through cuts and mucus membrane
• Placental transmission from the mother to the baby

3. Human biology
Disease
• During surgical operation with infected instruments
Treatment --- symptomatic
Prevention ---
• Avoid multiple sexual partners
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• Use sterilize surgical instruments
2012
• Screen blood before transfusions
• Avoid pregnancy if the person is sex worker
• Use condom during sexual intercourse
• Identify cases and isolate them
• Use sterilize syringe [needle]
• Avoid using same needles for different persons in hospitals and among drug abusers
• Burn all the personal belongings of the infected person after death
• Provide health education
• Poliomyelitis
Causative agent --- polio virus [it affects children between the age group of 0-5]
General information:
• This disease is becoming less common due to wide spread use of prophylactic immunization by oral
vaccines.
• The polio virus attack the spinal cord, brain stem & cortex [CNS]
• The polio virus eats up the nerve cells
• Unfortunately, the nerve cells cannot regenerate / recover. So the damage done is permanent
• Polio vaccine is a live attenuated- vaccine
Incubation period – from seven to fourteen days
Mode of transmission ---
• By droplet infection
• Oro-faecal route – through contaminated finger, water, milk, food, flies
Symptoms –
The virus enters through the respiratory tract, i.e. though the nasopharynx. Ai the onset, there is a mild
headache and pyrexia. This is followed by neck stiffness and meningeal irritation. Paralysis may occur later.
Treatment ---
• In the early stages bed rest is required
• Paralysis is the greatest at the end of the 1 st week of the major disease
• Gradual recovery may take place for several months but any muscle showing no sign of recovery by the
end of the month will not regain useful function
• Death may occur due to respiratory paralysis
Prevention – By oral vaccination between the age of 3 to 6 months and after one year
Oral vaccine --- small pox

4. Human biology
Disease
Bacterial diseases
• Diseases caused by bacteria:
Cholera, tuberculosis [TB], Lyme disease, pertussus, salmonella, staph infections, streep
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throat, leprosy, tetanus, diphtheria, E. coli, flesh eating [necrotizing fasciitis] & rickets
• Cholera2012
Causative agent --- bacteria [vibrio cholerae]
Mode of transmission – [water and food borne disease]
• Untreated sewage reaching a water source and the water consumed without proper treatment / chlorination
• Infected shell fishes or algae from water contaminated with untreated sewage
• Houseflies that sit on untreated sewage as well as food for humans and transmit bacteria into food
• Careless attendance of patients, contaminate themselves and spread the disease
• Incubation period: 2-6 days
Sign and symptoms –
• Diarrhoea and vomiting
• Fever muscle cramps weakness and even death if not rehydrated
Treatment –
• ORS [oral rehydration saline]: to replace water and electrolytes lost during diarrhoea
• Antibiotic: e.g. tetracycline to kill bacteria. Drugs like-Chloren phenicol and sulphur diazole
Prevention of spread –
• Prevent excess houseflies [since houseflies sit on sewage as well as human food] by:
• Killing them with insecticides
• Keeping the food covered / inside fridge
• Hygiene disposal of faeces since patients pass bacteria in faeces
• Supply of clean and safe drinking water since bacteria is transmitted in water
• Isolation of the patient
• Tuberculosis [TB]
Causative agent – Mycobacterium tuberculosis [they break down lung tissue]
This bacterium is of 3 types:
• Human type – causes pulmonary tuberculosis in lungs
• Bovine type – cause TB in cattle
• Atypical type – seen mostly in children
• A carrier is more dangerous than a case
• Carrier is an infected person showing no signs & symptoms
• A carrier ca discharge the germs through the fingers, nails, and faeces to make them get infected
unknowingly
Mode of transmission –

5. Human biology
Disease
• By air borne droplet infection
• When an infected person sneezes, sputum,, coughs, or even breaths, he spreads a fine spray of
pathogens
• The pathogens enter into the air and takes up a layer of moisture producing droplets
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• When a healthy person encounters these droplets through the nasal root is infected
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• Sputum from an open or sputum causative [positive] pulmonary TB patient to the primary source of
infection.
• Milk form infected cattle and its products are the source of infection
Symptoms ---
Persistent cough, breathlessness, fever, weight loss, generalized weakness
Treatment ---
• Patient must be hospitalized because side effects in most cases are quite severe
• Combinations of antibodies are given for six to nine months with enough vitamins & iron supplements
• Common drugs are: Streptomycin, INH [isoniazide], and Rifanpicin
Q: WHY A COMBINATION OF DRUGS ARE NECESSARY?
The TB bacteria like influenza virus can mutate to alter its structure or metabolism which makes an antibiotic
less effective or sometimes useless against the bacteria
Mutation makes the bacteria resistant against an antibiotic
This means that new antibiotics are to be used in a combination therapy to ensure effective treatment
Prevention –
• Inject BCG vaccine to all new born
• Pasteurized cattle milk before drinking
• This makes the TB bacteria unable to adjust to the frequent fluctuations of temperature making them die
• Avoid overcrowded places
• Avoid poorly ventilated areas / housing
• Maintain personal hygiene
• Promote health education
• Improvement of socio economic condition
Added information –
• TB is most common in amongst people who have a poor lifestyle quality
• Suffering from some levels of poverty
• They have poor / weak immune system which makes more vulnerable to develop TB
• Typhoid [bacterial disease]
Causative agent --- salmonella typhi

6. Human biology
Disease
Mode of transmission --- by drinking water contaminated with human faeces, or by flies transferring the
bacterium form the faeces to food
Incubation period --- about 2 weeks
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Symptoms ---
2012
A high fever, headaches, a cough, and a general feeling of being unwell
This disease develops over the following weeks, when the patient suffers stomach cramps, constipation, or
diarrhoea, vomiting and delirium [mental confusion]
Diarrhoea leads to several dehydration
Treatment ---
Vaccines against typhoid are available, and antibiotics such as penicillin are effective against the bacteria.
Oral rehydration therapies are effective against the bacteria. Oral rehydration therapy is effective. In
counteracting the effects of dehydration caused by diarrhoea.
Prevention ---
Good sanitation and hygiene is essential.
It only spreads in places where human faeces or urine come in contact with the food or drinking water
Q: How are viruses treated?
• Vaccines which prevent the host from contracting the virus
• Antiviral drugs which treat the virus once contracted
• Viral diseases can be very difficult to treat because the viruses have no metabolism of their own. Hence
antibiotics have no effect on them
Q: How are bacteria transmitted?
• Direct contact with an infected person
• Contaminated food or water [salmonella, E. coli]
• Dirty objects [tetanus]
• Infected animals [rabies]
Q: How are bacteria harmful?
Terrorism, disease, tooth decay, food spoilage
Q: How are bacteria helpful?
Antibiotics, nitrogen fixing, food, tanning leather, breaking down waste products, digestion
Treatment for bacterial infections ---
Antibiotics : a chemical substance that stops the growth of some micro-organisms such as bacteria within the
body
Or, they are compounds that block the growth and reproduction of bacteria
Sterilization : [heat] making something completely free of germs; or making an organism incapable of
reproduction

7. Human biology
Disease
Or, it is a way of destroying all bacteria by subjecting them to great heat
Pathogens : they are disease causing agents
Q: What are the 2 general ways that bacteria cause diseases?
• Some damage the tissues of the infected organism directly by breaking them for food
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• Others release toxins that harm the body
2012
After infection, a pathogen must do three things to produce a disease:
Attachment, entry [penetration], colonization
HOST – an organism in which another organism lives and gets nourishment and protection
Food borne infections including salmonella can spread in 2 ways:
• By not cooking food thoroughly E.g. raw eggs, newly laid eggs may be contaminated
• By contaminating cooked meat form handling raw meat first
• Air borne infections are spread when an infected person coughs, sneezes, talks or breaths, as the pathogens
are passed into the air in small droplets, saliva, mucus and water
• Insect bites can transmit pathogens through the saliva of the insect
After a person has been infected with a disease, there is an incubation period.
SIGN SYMpTOM
A sign of a disease is visible to other people. It can be A symptom is not usually visible to other people. It is
seen heard or measured what the patient experiencing as a result of the
disease, such as pain, chills, dizziness or nausea
FUNGAl DISEASES ---
Athletes foot Thrush
Causative agent: tinea like ringworm Causative agent: Candida albicans
Symptoms – Symptoms:
Forms white patches over the skin which are Red inflammatory patches over the skin or moist
generally circular mucus membrane e.g. mouth, vagina
May sometimes irritate
• Athletes foot and thrush are most common in individuals who are known to go through a major surgery
and taking a long term antibiotic course
• Thrush is more common in hospitals
• Thrush spreads through the infected bed sheets, pillow covers of the hospitals
Mode of transmission ---
Through skin to skin contact e.g. 1. Sharing of foot wears & undergarments [socks, under wears, stockings,
towels]
2. In public places e.g. gyms [gymnasium], foot mats [public toilets, food bath, sports changing room]
General information: fungi grows best in moist damp conditions
3. through infected pets
4. Sex workers [prostitutes]

8. Human biology
Disease
Treatment ---
Anti – fungal ointments, tablets/ drugs
Prevention ---
• Avoid using nd
Jul. 22 personal belongings of infected individuals [undergarments]
2012
• Avoid going to public places which is overcrowded
• Identify cases
• Treat infected pets
• Avoid multiple sex partners
Amoebic Dysentery
Causative agent: Amoeba (Entamocba histolytica)
Mode of transmission: 1. Water Borne Disease
Drinking or washing fruits &salads water cominated by untreated sewage.
2. Houseflies & cockroaches the transmit cyst of moeba to fppd
Sign & symptoms: 1. Diarrhoea & vomiting
2.Ulceration & bleeding of the intestine
3. It can lead to kidney failure & death due to deny dration.
Treatment: ORS to replace the water & electrolyte lost due to diarrhoea & vomiting.
Drugs like metronialozole followed by iodoquinol.
Prevention or spread: 1. Supply of clean & safe drinking water
2. Hygieric disposal of faeces
3. Proper sewage treatment
4. Prevent houseflics & cockroaches reaching food by keeping food
covered or in the refrigerator.
Q: How can dehydration lead to kidney failure?
• Dehydration is the result of a loss of excesoive salt & water
• Dehydration leads to decrease of blood volume
• The kidney purifies blood & to do so requires high pressure
• Impure blood enters into the kidney via renal artery at a low pressure leads to the failure of
kidney.
Bilharzia (parasitic disease)
Schistosoma causes bilharziasis. It is a parasite flatworm.
Life-cycle: The adult schistosoma lives in the hepatic portal vein or blood vessels leading to the
bladder. The male is larger than the female so the male carries the female on it. Eggs are laid in
the blood vessel. The eggs have a spiny covering. As the eggs mature it vibrates &penetrates the

9. Human biology
Disease
wall of the blood vessel & enters the blood stream. They are excreated out of the body along with
the urine & facecs.
The eggs are released in fresh water. The egg hatches producing the miracicluim larkae which can
not survive nd they do not enter a snail & are released. If the cerceriac larvae has to survive it has
if
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to enter a human body with 1 to 2 days. They can enter the human body by:
2012 1. If untreated water is swallowed.
2. It can also penetrate the skin of the ankle by enzyme reaction.
The larfirst enters the lymphatic system & then into the venous system & eventually into the
circulation. It takes about 23 days for the larvae to become an adult. The adult then establishes it on the
blood vessels.
Treatment: Give anti-biotic drugs
1. Nilodin
2.Miracil-D
Prevantion / Control-
1. Mapping an area for the sources of water with which people comes in contact. If snails are found
they should be checked for contain