Viruses are submicroscopic ions with cellular infectivity, consisting of a segment of DNA or RNA wrapped in a protective casing, and there are a wide variety of viruses that cause fever. First, there are mainly respiratory viruses, such as rhinovirus, influenza virus, parainfluenza virus, adenovirus, respiratory syncytial virus, measles virus coxsackievirus. Second, viruses of insects and hemorrhagic fever virus, epidemic encephalitis B virus, dengue fever virus, hemorrhagic fever virus, Ebola virus, hantavirus. Third, rabies virus, human immunodeficiency virus. Fourth, hepatitis viruses, hepatitis A virus, hepatitis B virus, and hepatitis C virus. Fifth, herpes viruses, herpes simplex virus, herpes zoster virus, cytomegalovirus, and other types such as human papilloma virus, rotavirus, and coronavirus.