| Epstein–Barr virus infection | |
|---|---|
| Other names | Immunodeficiency 32B[1] |
| Specialty | Infectious diseases  |
There are several forms ofEpstein–Barr virus (EBV) infection. These include asymptomatic infections, the primary infection,infectious mononucleosis, and the progression of asymptomatic or primary infections to:1) any one of variousEpstein–Barr virus-associated lymphoproliferative diseases such aschronic active EBV infection, EBV+hemophagocytic lymphohistiocytosis,Burkitt's lymphoma, andEpstein–Barr virus positive diffuse large B-cell lymphoma, not otherwise specified);[2]2) non-lymphoid cancers such asEpstein–Barr virus associated gastric cancer,[3] soft tissuesarcomas,leiomyosarcoma, andnasopharyngeal cancers;[4] and3) Epstein–Barr virus-associated non-lymphoproliferative diseases such as some cases of theimmune disorders ofmultiple sclerosis andsystemic lupus erythematosis[5] and the childhood disorders ofAlice in Wonderland Syndrome[6] andacute cerebellar ataxia.[7]
Symptoms ofinfectious mononucleosis arefever,sore throat, and swollenlymph glands. Sometimes, a swollenspleen orliver involvement may develop.Heart problems or involvement of thecentral nervous system occurs only rarely, and infectious mononucleosis is almost never fatal. There are no known associations between active EBV infection and problems during pregnancy, such as miscarriages or birth defects.[8][9] Although the symptoms of infectious mononucleosis usually resolve in 1 or 2 months, EBV remains dormant or latent in a few cells in the throat and blood for the rest of the person's life. Periodically, the virus can reactivate and is commonly found in the saliva of infected persons. Reactivated and post-latent virus may pass theplacental barrier in (alsoseropositive) pregnant women viamacrophages and therefore can infect the fetus. Also re-infection of prior seropositive individuals may occur. In contrast, reactivation in adults usually occurs without symptoms of illness.
EBV also establishes a lifelong dormant infection in some cells of the body's immune system. A late event in a very few carriers of this virus is the emergence of Burkitt's lymphoma and nasopharyngeal carcinoma, two rarecancers. EBV appears to play an important role in thesemalignancies, but is probably not the sole cause of disease.
Most individuals exposed to people with infectious mononucleosis have previously been infected with EBV and are not at risk for infectious mononucleosis. In addition, transmission of EBV requires intimate contact with the saliva (found in the mouth) of an infected person. Transmission of this virus through the air or blood does not normally occur. The incubation period, or the time from infection to appearance of symptoms, ranges from 2 to 6 weeks with 4 weeks being the most common. Persons with infectious mononucleosis may be able to spread the infection to others for a period of weeks. However, no special precautions or isolation procedures are recommended, since the virus is also found frequently in the saliva of healthy people. In fact, many healthy people can carry and spread the virus intermittently for life. These people are usually the primary reservoir for person-to-person transmission. For this reason, transmission of the virus is almost impossible to prevent.
The clinical diagnosis of infectious mononucleosis is suggested on the basis of the symptoms of fever, sore throat, swollen lymph glands, and the age of the patient. Usually, laboratory tests are needed for confirmation. Blood test results for persons with infectious mononucleosis include an elevatedwhite blood cell count, an increased percentage of atypical mononuclear cells. Liver enzymes are often elevated. A positive "mono spot" test is useful in confirming the diagnosis but a negative result does not rule out primary EBV infection.
Epstein–Barr can causeinfectious mononucleosis, also known as 'glandular fever', 'mono' and 'Pfeiffer's disease'. Infectious mononucleosis is caused when a person is first exposed to the virus during or after adolescence. It is predominantly found in the developing world, and most children in the developing world are found to have already been infected by around 18 months of age. Infection of children can occur when adults mouth feed or pre-chew food before giving it to the child.[12] EBVantibody tests turn up almost universally positive. In theUnited States roughly half of five-year-olds have been infected.[13]
The strongest evidence linking EBV and cancer formation is found inBurkitt's lymphoma[14]andnasopharyngeal carcinoma. Additionally, it has been postulated to be a trigger for a subset ofchronic fatigue syndrome patients[15] as well asmultiple sclerosis and otherautoimmune diseases.[16]
Burkitt's lymphoma is a type ofNon-Hodgkin's lymphoma and is most common inequatorial Africa and is co-existent with the presence ofmalaria.[17] Malaria infection causes reduced immune surveillance ofB cells immortalized by EBV, resulting in an excessive number of B cells and an increased likelihood of an unchecked mutation. Repeated mutations can lead to loss of cell-cycle control, causing excessive proliferation observed as Burkitt's lymphoma. Burkitt's lymphoma commonly affects thejaw bone, forming a huge tumor mass. It responds quickly tochemotherapy treatment, namelycyclophosphamide, but recurrence is common.
Other B cell lymphomas arise in immunocompromised patients such as those withAIDS or who have undergone organ transplantation with associatedimmunosuppression (Post-Transplant Lymphoproliferative Disorder (PTLPD)).Smooth muscle tumors are also associated with the virus in malignant patients.[18]
Nasopharyngeal carcinoma is a cancer found in theupper respiratory tract, most commonly in thenasopharynx, and is linked to the EBV virus. It is found predominantly inSouthern China and Africa, due to both genetic and environmental factors. It is much more common in people of Chinese ancestry (genetic), but is also linked to the Chinese diet of a high amount of smoked fish, which containnitrosamines, well knowncarcinogens (environmental).[19]
EBV can be diagnosed through aserological test which detectsantibodies in the blood. A serological test should not be conducted among patients withantibody deficiencies and/or passive antibodies. Another test involves screening for the measurement of EBVviral loads inperipheral blood.Radiographic testing is often paired with EBV viral load measuring. Abiopsy can also be conducted in order to find where the EBV is manifested.[20][21]
There is no specific treatment for infectious mononucleosis, other than treating the symptoms. In severe cases, steroids such ascorticosteroids may be used to control the swelling of the throat and tonsils. Currently, there are no antiviral drugs orvaccines available.
It is important to note that symptoms related to infectious mononucleosis caused by EBV infection seldom last for more than 4 months. When such an illness lasts more than 6 months, it is frequently called chronic EBV infection. However, valid laboratory evidence for continued active EBV infection is seldom found in these patients. The illness should be investigated further to determine if it meets the criteria forchronic fatigue syndrome, or CFS. This process includes ruling out other causes of chronic illness or fatigue.