Epidemiology - Epstein Barr Virus

Epidemiology

Epstein–Barr virus infection occurs worldwide, but since it is not a reportable infection, the exact prevalence of infection is not known.

◗ Geographical distribution

The viral infection is of relatively low transmissibility and does not occur as epidemics. It has been estimated that by age of 5 years, approximately 50% of the population in the United States is infected by EBV. The same appears to be true for other developed countries. In developing countries, 90% of children below 5 years are believed to experience an asymptomatic EBV infection.

Reservoir, source, and transmission of infection

Epstein–Barr virus infection is exclusively a human disease. Humans are the only known reservoirs of the virus. It is pres-ent in oropharyngeal secretion, saliva, peripheral blood, or lymphoid tissue of the infected human host. Saliva is the main source of infection. The saliva of people with active infection as well as people with reactivation of a latent infection constitute major source of infection. More than 90% of EBV-infected peo-ple intermittently shed the virus in their saliva throughout the life even when totally asymptomatic. The virus causes lifelong infection. The infection is transmitted by:

·           saliva through close oral contact during the act of kissing;

·           sharing of items, such as drinking glasses, cups, tooth-brushes, etc.;

·           blood transfusion and by bone marrow transplantation, but rarely.

The possible association of cofactors is suggested to play an important role in the geographical distribution of EBV-associated tumors. Malaria has been suggested as an important cofactor in the progression of chronic or latent EBV infection to acute Burkitt’s lymphoma in Africa. The genetic predisposi-tion of the people in China or the presence of cofactors in the food or environment is believed to be important in facilitating the incidence of nasopharyngeal carcinoma in people living in certain parts of China.

Immunocompromised people, such as patients with AIDS, transplant recipients, and genetically immunodeficient peo-ple are at high risk for lymphoproliferation disorders caused by EBV.