The Epstein–Barr virus (EBV), also called human herpesvirus 4 (HHV-4), is one of eight known human herpesvirus types in the herpes family, and is one of the most common viruses in humans.
It is best known as the cause of infectious mononucleosis ("mono" or "glandular fever"). It is also associated with particular forms of cancer, such as Hodgkin's lymphoma, Burkitt's lymphoma, gastric cancer, nasopharyngeal carcinoma, and conditions associated with human immunodeficiency virus, such as hairy leukoplakia and central nervous system lymphomas. Some evidence indicates infection with EBV is associated with a higher risk of certain autoimmune diseases, especially dermatomyositis, systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, and multiple sclerosis. About 200,000 cancer cases per year are thought to be attributable to EBV.
Infection with EBV occurs by the oral transfer of saliva and genital secretions.
Most people become infected with EBV and gain adaptive immunity. In the United States, about half of all five-year-old children and about 90% of adults have evidence of previous infection. Infants become susceptible to EBV as soon as maternal antibody protection disappears. Many children become infected with EBV, and these infections usually cause no symptoms or are indistinguishable from the other mild, brief illnesses of childhood. In the United States and other developed countries, many people are not infected with EBV in their childhood years. When infection with EBV occurs during adolescence, it causes infectious mononucleosis 35 to 50% of the time.
EBV infects B cells of the immune system and epithelial cells. Once EBV's initial lytic infection is brought under control, EBV latency persists in the individual's B cells for the rest of the individual's life.