Question

List various causes of diseases.

Answer 1

The means of spread or cause of communicable diseases are different for different pathogens.
I. The disease causing microorganisms (pathogens) are transmitted from infected person to healthy person(s) directly by physical contact with infected person. The pathogens of diseases like chicken pox, small pox, ring worm etc. are spread through physical contact with infected person or through articles of use.
2. Few infectious diseases such as syphilis, gonorhoea (both caused by bacteria) and AIDS (caused by virus) are transmitted 'by sexual contact from one partner to the other.
3. Many pathogens can enter the human body from soil through injuries (e.g. tetanus).
4. Communicable diseases can also spread through the animal bites. For example, rabies virus enters the human body by the bite of rabid dog or monkey to cause rabies.
5. Indirect transmissions involves spread of pathogens. of some diseases through some intermediate agents. Indirect transmission occurs through air.
6. The infected person throws out little droplets on sneezing, coughing or spitting. Someone standing close by can breathe in these droplets and, thus, microbes get a chance to start a new infection in this person.
7. Many animals living with us carry the infecting agents from an infected person to other potential host. These animals act as intermediaries and are termed vectors. The vectors are, therefore, the carriers of the disease. causing pathogens. The most common vectors are the insects.