Both bacteria and a virus will do no good to your body, but theres a difference to what the do to you, how they enter your body or other systems, what symptoms they can cause you, and what you can do about it. Bacteria is a single celled microorganism that usually enters through your mouth. Bacteria can survive in multiple types or environments and will give you things such as strep throat or tuberculosis. A virus is much smaller than bacteria and needs a living host to reproduce. Unlike bacteria, viruses can enter your body in versus ways. What the virus will do is it will highjack your body and reprogram your cells to start reproducing the virus. They can give you symptoms such as chicken pox and most famously, types of colds.