Page 6 - 2. Lesson Notes- Infectious Disease

● There are a few infectious agents that go to a particular organ and then spread

throughout the body. The HIV virus enters the body through sexual contact and
tends to spread to lymph nodes throughout the body.

● The malarial parasite enters the liver and spreads to the red blood cells. The signs
and symptoms of disease thus depend upon the tissue or organ it targets.

Tissue-Specific Manifestation

• The immune system is also activated in response to infections. The
microorganisms enter into the tissues and damage it.

• The immune system recruits the disease-causing microbes and destroys them.
This is known as inflammation. The severity of disease manifestations depends

upon the number of microbes in the body.

• The immune system keeps a check on the number of microbes in the body. When
the immune system is damaged due to a deadly virus like HIV, the body can no

longer fight the infections and the patient does not survive for long.

Pathogen Point of entry Target organ Diseases caused

Bacteria Nose Lungs, can attack Tuberculosis
(Mycobacterium any part of the body

tuberculosis) such as kidney,
spine, brain

Virus Blood stream Brain Japanese

encephalitis, or brain
fever

Virus(hepatitis A, Mouth Liver Jaundice
hepatitis B.

hepatitis C)

Virus (Acquired Liver, and then to the Lymph nodes AIDS
immunodeficiency red blood cells.

virus)