Page 5 - 2. Lesson Notes- Infectious Disease

and water. Disease causing organisms and harmful pollutants in the form of

chemicals can easily enter the body through food and drinks.
3. Sexually-transmitted diseases, STDs: These infections pass from infected

person to healthy one through sexual contact. The causes of STDs are bacteria
and viruses. Infectious diseases such as syphilis, Gonorrhoea (caused by bacteria)

and AIDS from one partner to the other. (caused by virus) are transmitted by sexual

contact f
4. Through vectors: (example- malaria,

dengue)
Many animals which live with us may

carry diseases. Such animals or insects

that carry infectious diseases from sick
person to another potential host and

spread a disease are called vectors.
These animals act as intermediaries and

are the carriers of the disease causing pathogens.

Organ-specific and tissue-specific manifestation:

• Organ and tissue-specific manifestations refer to certain organs, tissues, or cells
where the microorganisms affect a person’s body.

• When the microbes affect the entire organ, such as lungs or kidneys, it is known
as organ-specific manifestation.

• When the entire tissue is affected by the microbes, it is called a tissue-specific

manifestation.
Organ-Specific Manifestation

● The microorganisms that enter the body travel to a specific organ and multiply

there. Mycobacterium tuberculosis is the bacteria that causes tuberculosis. It
usually enters the body through the nose and migrates to the lungs.

● Bacteria such as the Salmonella enter through the mouth (through consumption of
infected food or water) and travels to the gut lining causing yphoid.