Major advances in molecular virology have led to the development of new antiviral compounds. These drugs include ribavirin, used in the treatment of severe respiratory syncytial virus infection in children; amantadine, used in the prophylaxis and treatment of influenza A infection; acyclovir, used in a variety of herpesvirus infections, including primary gingivostomatitis, genital herpes and herpes zoster; ganciclovir, used in the treatment of retinitis due to cytomegalovirus, and zidovudine, used in the prophylaxis and treatment of human immunodeficiency virus infection.