EPSTEINBARR VIRUS

also called Eb Virus, or Ebv, a herpes virus that is the major cause of acute infectious mononucleosis, a common syndrome characterized by fever, sore throat, extreme fatigue, and swollen lymph glands. EBV was first reported by British scientists M.A. Epstein, Y.M. Barr, and B.G. Achong, who found viruslike particles in cells grown from tissues involved with a newly described lymphatic cancer. The EpsteinBarr virus is known to be able to infect only two different types of cells in the body: some salivary gland cells and one special type of white blood cell. Virus that grows in the salivary gland cell is carried into the mouth in the stream of saliva. Saliva is the only bodily fluid that has been proved to contain infectious EBV particles. The type of white blood cell called the B lymphocyte can also carry EpsteinBarr virus. These highly specialized cells manufacture antibodies to help fight infections. Within the salivary gland the virus growth cycle is completed and infectious virus particles are generated; within the B lymphocytes, however, the virus growth cycle is abortive, and the EBV persists in the B lymphocyte in a partially replicated state for the life of the cell. Even though the virus growth in the B cell is incomplete, the lymphocyte is permanently altered by the infectious processi.e., B cells take on growth characteristics that resemble those of cancerous lymphocytes. The affected B lymphocytes can multiply excessively to produce a cancer of the lymphatic system. In the less-developed nations, infection with EBV occurs in almost all children before the age of five and is not associated with any symptoms, or certainly none typical of infectious mononucleosis. In industrialized nations about half of the people successfully avoid EBV infection through their late teens or early 20s. When EBV infection is delayed until the teenage or early adult years, the body seems to respond to it differently. In about two-thirds of these cases infection is asymptomatic or very mild. In the remaining one-third of the cases, infection causes infectious mononucleosis. Other, rarer disorders have also been linked with EpsteinBarr virus. These include the African lymphoid cancer called Burkitt's lymphoma; nasopharyngeal carcinoma, a cancer of the nasal sinuses and throat that is common in southern China, Southeast Asia, northern Africa, and among Eskimos; and certain uncommon but severe neurological illnesses, including encephalitis (inflammation of the brain) and paralyses of various nerve groups (for example, Bell's palsy, which affects the facial nerve). Recent scientific evidence suggests that some individuals who develop EBV infection do not recover within the usual time of days to weeks that is typical of acute infectious mononucleosis. They may partially recover but continue to experience fatigue, intermittent sore throats, tender lymph nodes, and feverishness. The association of this disordersometimes called chronic mononucleosis, chronic fatigue syndrome (CFS), or chronic EpsteinBarr virus (CEBV)with the EpsteinBarr virus is still hypothetical. There are no specific treatments for any form of EBV infection, and no vaccines have yet been developed.