Microbes and the human body


The surfaces of the human body inside and out, for example the skin, mouth and the intestines, are covered in millions of individual micro-organisms that don’t do us any harm. In fact they help to protect us from becoming infected with harmful microbes. They are known as the normal body flora.

The number of normal bacterial cells that live on the body is in the region of 100 million. This number is 10 times greater than the 10 million cells that make up the human body.


  • Microbes and disease

    Microbes that cause disease are called pathogens. Find out which microbe is responsible for malaria!

  • Immune system

    An infection can be seen as a battle between the invading pathogens and host. How does the immune system work?

  • Routes of transmission

    Find out how you can pick up germs and pass them on to others.

  • Vaccination

    Just a shot in the arm – what do vaccines do?

  • Antibiotics

    Antibiotics are powerful medicines that only fight bacterial infections.

Thumbnail image credit: iStock/Dr_Microbe