But there is probably an explanation for each of their histories. Uncovering these answers will help in establishing a prevention strategy. Exposure and susceptibility to infections Infection occurs when a disease-causing germ such as a bacteria, virus or fungus invades the body. Exposure is something that your grandmother warned you about when she told you to stay away from Johnny because he was sick. Those in positions with a lot of people contact, such as elementary school teachers or salespersons, are more likely to be exposed to increased numbers of germs.
Susceptibility is more complicated than exposure.
We are all susceptible to infection by thousands of different germs. The purpose of the immune system is to prevent infection by recognizing germs and eliminating or disabling them before they can cause infection. Some germ families have faces that are so similar that when your immune system learns the face of one member of the family, it protects you from infection by any member of that family. Other germ families are so different that the immune system must learn each face individually. Once your immune system has learned the face of a particular germ and successfully battled it, you are no longer susceptible to infection caused by that germ.