This virus causes an acute febrile illness known as infectious mononucleosis (glandular fever), which occurs world-wide in adolescents and young adults. EBV is probably transmitted in saliva and by aerosol.

Clinical features

The predominant symptoms are fever, headache, malaise and sore throat. Palatal petechiae and a transient macular rash are common, the latter occurring in 90% of patients who have received ampicillin (inappropriately) for the sore throat. Cervical lymphadenopathy, particularly of the posterior cervical nodes, and splenomegaly are characteristic. Mild hepatitis is common, but other complications such as myocarditis, meningitis, encephalitis, mesenteric adenitis and splenic rupture are rare.

Although some young adults remain debilitated and depressed for some months after infection, the evidence for reactivation of latent virus in healthy individuals is controversial, although this is thought to occur in immunocompromised patients. Following primary infection, EBV remains latent in resting memory B lymphocytes. It has been shown in vitro that of nearly 100 viral genes expressed during replication, approximately only 10 are expressed in the latently infected B cells. Severe, often fatal infectious mononucleosis may result from a rare X-linked immunoproliferative syndrome affecting young boys. Those who survive have an increased risk of hypogammaglobulinaemia and/or lymphoma.

EBV is the cause of oral hairy leucoplakia in AIDS patients and is the major aetiological agent responsible for Burkitt's lymphoma, nasopharyngeal carcinoma, post-transplant lymphoma, and the immunoblastic lymphoma of AIDS patients and Hodgkin's lymphoma. Different levels of expression of EBV latency genes occur in the various clinical conditions caused by the virus.

Diagnosis

EBV infection should be strongly suspected if atypical mononuclear cells (glandular fever cells) are found in the peripheral blood. It can be confirmed during the second week of infection by a positive Paul-Bunnell reaction, which detects heterophile antibodies (IgM) that agglutinate sheep erythrocytes. False-positives can occur in other conditions such as viral hepatitis, Hodgkin's lymphoma and acute leukaemia. The Monospot test is a sensitive and easily performed screening test for heterophile antibodies. Specific EBV IgM antibodies indicate recent infection by the virus. Clinically similar illnesses are produced by CMV and toxoplasmosis but these can be distinguished serologically.

Treatment

The majority of cases require no specific treatment and recovery is rapid. Corticosteroid therapy is advised when there is neurological involvement (e.g. encephalitis, meningitis, Guillain-Barré syndrome) or when there is marked thrombocytopenia or haemolysis.