Viruses and bacteria are two completely different organisms and are more different than being similar. However, both are microscopic organisms that require a microscope to be seen, can cause diseases, and both can exist by themselves.
Viruses are usually much smaller than bacteria and need to attach to a living cell to reproduce. They also commonly cause disease and attack healthy cells in the body. On the other hand, bacteria can reproduce in many places and don't need to be with a living cell to reproduce. Also, less than 1% of bacteria cause disease in humans, most bacteria are actually helpful for humans, unlike viruses.