Overview of Herpesvirus Infections

Some common viral infections are caused by a group of viruses called herpesviruses. Eight different types of herpesviruses infect people:

• Three herpesviruses—herpes simplex virus type 1, herpes simplex virus type 2, and varicella-zoster virus (herpesvirus type 3, which causes chickenpox and shingles)—cause infections that produce blisters on the skin or mucus membranes.

• Epstein-Barr virus (herpesvirus type 4) causes infectious mononucleosis and may be involved in certain cancers (such as nasopharyngeal cancer, Burkitt lymphoma, and Hodgkin lymphoma).

• Cytomegalovirus (herpesvirus type 5) is a cause of serious infections in newborns and in people with a weakened immune system. It can also cause symptoms similar to infectious mononucleosis in people with a healthy immune system.

• Human herpesviruses 6 and 7 cause a childhood infection called roseola infantum.

• Human herpesvirus 8 causes certain cancers (Kaposi sarcoma and some types of lymphoma), in people with a weakened immune system such as people with advanced infection with human immunodeficiency virus (HIV).

All of the herpesviruses cause lifelong infection because the virus remains within its host cell in an inactive (dormant or latent) state. During the dormant phase, herpesviruses evade detection by the immune system. Sometimes the virus reactivates and produces further episodes of disease. Symptoms from reactivation can be different than the symptoms of the initial infection. Reactivation may occur rapidly or many years after the initial infection. (See also Overview of Viral Infections.)