Experts believe that there are more viruses than any other types of organism, and they parasitize recognized life forms (even bacteria). More than 200 types of viruses have been identified that cause human disease, including the adenovirus, arenavirus, coronavirus, enterovirus, herpesvirus, poxvirus, picornavirus, rhinovirus, and retrovirus.
Viral infections may be mild (such as the common COLD or WARTS), or they can be extremely serious, such as RABIES, AIDS, SMALLPOX, POLIO, and probably some types of cancer.
There are no specific cures for viral diseases, although some of the newest antiviral drugs can treat symptoms and lessen the seriousness of viral infections. However, it is possible to prevent some of the viral diseases through vaccination, including
smallpox, MEASLES, and polio.