Human beings have enemies far too small to be seen under a microscope. These enemies are known as microorganisms. An extremely large number of microorganisms live in our body. Some of these microorganisms even help us in carrying out various body functions. Although most microorganisms are harmless to us but some of them cause serious diseases. The disease causing microorganisms like bacteria, fungi, virus and protozoa enter our body parts through various means such as:

  1. Through the food and water that we use,
  2. Through the air we breathe,
  3. Through skin contacts and sexual contacts,
  4. Through lesions,

Through carries. The insects that carry disease-producing microorganisms from one host to another are called vectors. For example, mosquitoes and flies.

Cholera, gastroentritis and typhoid are caused by bacteria, which spread through food and water.

Common cold and influenza virus are spread through air.


Ringworm, a fungal infection spreads through direct skin contacts. Diseases such as syphilis, gonorrhoea and AIDS spread through sexual contact. These are known as sexually transmitted disease (STD).

Malaria, dengue amoebiasis and food poisoning spread through carries such as mosquitoes and files.

Now let us discuss some diseases caused by various microorganisms. Some common disease caused by microorganisms is given.

Causative Microorganism

  1. Bacteria
  2. Fungi
  3. Virus
  4. Diseases