Autoimmunity simply stated is one's immune system responding to self. The occurrence of infectious disease is affected by interaction between microorganisms. The link between certain bacterial infections and autoimmunity is particularly compelling, and molecular mimicry is often implicated in autoimmune disease pathogenesis. The role of microorganisms in the spreading of diseases has undergone significant modification in the past few decades with new observations from clinical, epidemiologic, and basic science research. Primary bacterial colonizers are Staphylococcus epidermidis and other coagulase-negative Staphylococci. Other microorganisms that are generally regarded as skin colonizers are species of Corynebacterium, Propionibacterium and Brevibacterium. Adenovirus, herpesvirus, and poxvirus are all examples of large DNA viruses that infect humans. Adenoviruses, of which there are many types, cause gastroenteritis and respiratory disease in humans. Notable human diseases caused by RNA viruses include the common cold, influenza, SARS, MERS, COVID-19, Dengue Virus, hepatitis C, hepatitis E, West Nile fever, Ebola virus disease, rabies, polio, mumps, and measles. Parasitic diseases that can be blood borne include African trypanosomiasis, babesiosis, Chagas disease, leishmaniasis, malaria, and toxoplasmosis. Vaccinations are generally the cheapest and most effective trusted Source way to prevent viruses. Some vaccines have succeeded in eliminating diseases, such as smallpox.