There are a wide variety of diseases out there but what causes these diseases. The answer is bacteria and viruses, each of these has a nasty way of effecting your body. Some of the differences between bacteria and viruses are there size, how often they come and go, and how each one affects your cells.
The first large difference is that viruses are over 100 times smaller than a bacteria. The reason for why viruses are smaller is because a bacteria is almost the same size as a cell. Therefore, a virus needs to get into a cell to infect. Making the virus smaller than the cell/ bacteria.
The next difference is that viruses are far more common, from throat pains to a stuffy nose. Viruses are more common because they can reproduce far faster than a bacteria.
A virus and a bacteria have two different ways of infecting a person. A virus plugs itself into a cell and then spits it's D.N.A into the cell. This cell then produces more viruses, then the cell pops releasing all of the new viruses. A bacteria is much different and will cling onto cells and then telling the cell to do the things the bacteria wants.