Class 9 Biology Why Do We Fall Ill Modes of transmission of disease

Modes of transmission of disease

The diseases that spreads from an infected person to a healthy and disease free person are called communicable diseases.

These diseases spreads when an infected person sneezes or coughs, they throw tiny droplets of water into the air that contains the microbes of the infection.

A healthy person standing nearby when inhale the air they take in the infected air and may fall sick.

Some example of communicable diseases are chicken pox, tuberculosis, Pneumonia, etc.

These diseases also spreads when the excreta of an infected person somehow gets mixed with drinking water used by other people to drink.

Diseases like cholera, typhoid spreads through this means and cause disease to a new host.

Communicable diseases also spread through sexual intercourse between an infected person and a healthy person.

Therefore, diseases like Acquired Immune Deficiency Syndrome (HIV/AIDS), syphilis are sexually transmitted diseases (STDs).

Acquired Immune Deficiency Syndrome (HIV/AIDS) can also spread through other means like blood-to-blood contact with an infected person by using same syringes in hospitals, or using same personal belongings (for example, razor, toothbrush, etc.).

Acquired immune deficiency syndrome (HIV/AIDS) can also spread to a healthy baby from their mother during pregnancy or by breast feeding.

Some diseases like skin infections, ringworm, conjuvitis are spread by direct contact with infected person through handshakes, touch or kiss.

Many diseases are carried from an infected person to a healthy person through animals. Such animals are called vectors.

Mosquitoes and houseflies are good examples of such vectors.

The female anopheles mosquito spreads Malaria whereas Female Aedes mosquito spreads Dengue.

Houseflies sits on garbage, drains, human and animal excreta and then flies off and sits on uncovered food consumed by healthy person. This way houseflues transmits the disease to the new healthy host.

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