Viruses, Bacteria & Parasites

Viruses, bacteria and parasites are living organisms that are found all around us. They exist in water and soil, on the surfaces of foods that we eat and on surfaces that we touch, such as countertops in the bathroom or kit​chen. Some bacteria live in our bodies and do not cause problems. Other kinds of bacteria (as well as parasites and viruses) can make us quite ill if they invade our bodies. Bacteria and viruses can live outside of the human body (for instance, on a countertop) sometimes for many hours or days. Parasites, however, require a living host in order to survive.

Bacteria and parasites can usually be destroyed with antibiotics. On the other hand, antibiotics cannot kill viruses. Children with viral illnesse​s can be given medications to make them comfortable, but antibiotics are ineffective against treating these infections.

Bacteria, viruses and parasites can cause a wide variety of illnesses, and can infect any of the organs of the body. Viruses are often responsible for respiratory illnesses (such as the common cold) and digestive illnesses (su​ch as diarrhea). Bacteria can infect any part of the body, but often cause diarrhea when they invade the digestive tract.


Diarrhea can be caused by a variety of bacteria, viruses and parasites. Children can also have diarrhea without having an infection, such as when diarrhea is caused by food allergies or as a result of taking medications (such as antibiotics). A child is considered to have diarrhea when the child's bowel movements ​are both more frequent than usual and looser and more watery than usual.

Children with diarrhea may ha​ve additional sympto​ms including nausea, vomiting, stomach aches, headache or fever.

Coming in ​Contact

Children can come in contact with bacteria, viruses and parasites in numerous ways, including the following:

  • When touching the stool of an infected person
  • When touching a contaminated object
  • By ingesting contaminated food or water