Epstein–Barr virus (EBV), also called human herpesvirus 4, is a double‑stranded DNA virus of the Herpesviridae family. It infects B lymphocytes and epithelial cells and is the primary cause of infectious mononucleosis.
Biology and Pathogenesis
EBV is a gamma herpesvirus with a DNA genome enclosed in an icosahedral capsid, a tegument and an envelope. After entering the oral cavity, the virus infects oropharyngeal epithelial cells and naive B lymphocytes. It then spreads through blood and lymphoid tissues. Replication in B cells leads to production of viral proteins that drive proliferation and immortalization. The host mounts a robust cytotoxic T‑cell response to control infection, resulting in the atypical lymphocytosis seen in mononucleosis. Once primary infection resolves, EBV genomes persist latently in memory B cells. Reactivation occurs sporadically, leading to asymptomatic viral shedding in saliva. Transmission occurs through exchange of saliva, earning EBV the colloquial name “kissing virus.” The virus is nearly ubiquitous; in many populations more than 90 percent of adults carry latent EBV. Although primary infection in childhood is often subclinical, infection during adolescence frequently causes infectious mononucleosis with fever, pharyngitis and lymphadenopathy. In immunocompromised hosts, EBV may drive uncontrolled B‑cell proliferation leading to lymphoproliferative disorders.
Notable Disease Associations
Infectious mononucleosis is a clinical syndrome characterized by fever, sore throat, swollen cervical lymph nodes and fatigue. Laboratory findings include lymphocytosis and the presence of heterophile antibodies. Most cases resolve with supportive care, but splenomegaly can predispose to rupture. EBV is associated with several malignancies. Burkitt’s lymphoma, a high‑grade B‑cell tumor endemic in parts of Africa, contains EBV DNA in the tumor cells. Nasopharyngeal carcinoma, prevalent in southeast Asia, is strongly linked to EBV infection of epithelial cells. The virus is implicated in Hodgkin’s lymphoma and some gastric carcinomas. Immunocompromised patients, such as transplant recipients or individuals with advanced HIV infection, may develop EBV‑driven lymphoproliferative disease or oral hairy leukoplakia. EBV is a gamma herpesvirus that infects B cells and epithelial cells, persists in latent form, and is transmitted via saliva. It causes infectious mononucleosis and is associated with several cancers and lymphoproliferative disorders. Control of EBV relies on cell‑mediated immunity, but no vaccine is currently available. Related Terms: Cytomegalovirus, Varicella‑Zoster Virus, Herpes Simplex Virus 1, Herpes Simplex Virus 2, Kaposi’s Sarcoma‑associated Herpesvirus