Epstein-Barr virus (EBV) is one of a number of herpes viruses. While the term "herpes" usually is considered to be a condition, caused by sexual contact, sexually transmitted herpes is only one of many herpes viruses. EBV is also called herpes virus 4, and it is most frequently recognized as one of the viruses most commonly responsible for mononucleosis (mono).
Contraction of EBV does not always mean a person will develop mononucleosis, however. Someone who is exposed to the virus as an adolescent typically has, at most, a 50% chance of developing the illness. People who are exposed can still pass the virus on to others, however, even if they don't develop mono themselves. The virus can also become dormant and reactivate years later; it usually does not cause symptoms once active again, but can be passed on to others.
Mononucleosis is most common in adolescents, and when contracted by children can result in symptoms like a fever, sore throat, and fatigue for a few weeks. Some children will have full-blown mono, which can last for up to four months, but many will never develop serious symptoms. Epstein-Barr virus is extremely prevalent, however, and most people show exposure to the virus by the time they reach adulthood.
Some research has suggested a connection between EBV and chronic fatigue syndrome, although the relationship is unclear. Mononucleosis symptoms which last for longer than six months are sometimes referred to as "chronic EBV," although many times tests do not find that the virus is still active. Many experts think that, in such cases, there may be other causes for chronic fatigue, especially since most people have been exposed to the virus and do not develop the condition.
Epstein-Barr virus may also be indicated in certain forms of cancer. EBV is frequently detected in those who have a form of non-Hodgkin's lymphoma, called Burkitt's lymphoma. The virus is also thought to be a causal factor of carcinomas in the nose and throat. These cancers are most commonly found in people living in third world countries. They may also be present in patients who are immunosuppressed, in the form of tumors found in the muscles surrounding organs.
Burkitt's lymphoma actually responds extremely well to chemotherapy, and often can be resolved by such, though occasionally tumors along the jaw can recur. Those who have immunosuppressive illnesses or who have received transplants may have a more difficult treatment and recovery, since chemotherapy to treat such tumors further suppresses the immune system. Fortunately, these tumors are relatively rare.