EBV is a member of the herpesviridae - the only human virus in the gamma herpesvirus subfamily (Lymphocryptovirus genus) As with all herpesviruses, EBV establishes lifelong persitent infections that may undergo periodic reactivation, particularly in immunosuppressed hosts.

It is estimated that over 90% of adults are seropositive for EBV. Infection usually occurs during childhood - many cases are asymptomatic. The virus is transmitted primarily by saliva - transmission by blood transfusion is rare. EBV is often found in the saliva of asymptomatic people.

Following primary infection with EBV, antibodies to a number of viral antigens appear in the bloodstream. Viral capsid antigen (VCA) is the primary marker used for the diagnosis of EBV infection. VCA IgM appears within the first week of infection and remains detectable for up to three months. VCA IgG appears within 4-7 days after onset of symptoms and may persist for life. Epstein-Barr nuclear antigen (EBNA) IgM antibodies are detectable for 3-6 days after onset of symptoms, often appearing before VCA IgM. EBNA IgG antibodies mark the transition from acute infection to convalescence and may persist for life. Early antigens diffuse (EA-D) IgG antibodies rise in the acute phase.