Q: What are bacteria and viruses?
A: Bacteria are single-celled organisms found all over the inside and outside of our bodies. Many bacteria are not harmful. In fact, some are actually helpful, including the majority of bacteria that live in our intestines (guts). However, disease-causing bacteria can cause illnesses such as strep throat. Viruses, on the other hand, are microbes that are even smaller than bacteria that cannot survive outside the body's cells. They cause illness by invading healthy cells.