This type of herpes is very different from both herpes simplex and varicella zoster. The Epstein-Barr virus (EBV) is also known as human herpes virus 4 (HHV-4). Rather than remaining dormant in the nerve cells after infection, EBV resides in B lymphocytes, a type immune system cell. Up to 95 percent of adults between the ages of 35 and 40, as well as half of all 5-year-olds, have been infected by EBV [source: CDC].
If a child is infected with EBV, he or she may just have mild flulike symptoms -- or no symptoms at all. Between 35 and 50 percent of mononucleosis cases in adolescents and young adults, however, are caused by EBV [source: CDC]. It's transmitted through saliva and is highly infectious. People with mono can expect high fevers, extreme fatigue, sore throat, loss of appetite, broken blood vessels in the eyes, and swollen lymph nodes and spleen. Treating mono equals lots of bed rest, fluids and pain relievers. Most of the symptoms usually clear up in two to four weeks, and the immune system suppresses any further occurrences of mono.
Most healthy people recover with no lasting effects, although there are some potential complications. The enlarged spleen can rupture and the liver can become inflamed and cause jaundice (yellowing of the skin). People with mono can become anemic or have some of the nervous system disorders caused by other types of herpes, such as encephalitis or myelitis. The risk of developing these complications is higher in people with weak immune systems.
In some people, mono doesn't go away after a month or even six months, at which point it's called chronic EBV infection. Some researchers have theorized that EBV may cause chronic fatigue syndrome, but this hasn't been proven. EBV has also been linked to two rare types of cancer: nasopharyngeal carcinoma and Burkitt's lymphoma. Nasopharyngeal carcinoma, which affects the respiratory tract, has been found primarily in China and North Africa. Burkitt's lymphoma occurs primarily in Africa and affects the jawbone. It often exists along with malaria because of the person's reduced immune system response. EBV has also been linked to lymphomas (cancer beginning in the immune system) in AIDS patients and other immune system disorders in organ transplant patients. A vaccine for EBV is currently in clinical trials.
Next, we'll look at another type of herpes virus that can cause mononucleosis: cytomegalovirus.