Microorganisms can cause disease, and their consequences are usually colds, pneumonia, sore throat, diarrhea, cold sores, hepatitis B and other diseases. Different diseases are caused by different pathogens. We summarize for you what is the difference between viruses and bacteria and how you can protect yourself. What are the differences between bacteria and viruses ? Both bacteria and viruses can cause disease, but there are differences. These are organisms that differ from the outside and whose origin and effects on the human body.