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Epstein Barr virus was discovered only in 1964, but it turned out to be one of the most common viruses in humans. By the age of 40 years old, around 90% of people get infected with this pathogen. If the infection is so common, how it comes that we hardly aware of its existence?
Most people get infected during childhood, often in infancy as soon as maternal antibody protection disappears. Infection often proceeds asymptomatically or manifests itself in the form of infectious mononucleosis. The symptoms of this disease include fever, sore throat and swollen lymph glands and can often be taken for other common infections. This is the reason why disease usually does not get correctly diagnosed and remains unnoticed.
Although EBV infection is relatively harmless, long-term consequences can be significant
Disease is almost never fatal and symptoms tend to disappear spontaneously in several weeks. The person remains, however, infected for life since the virus becomes dormant and avoids the body’s immune response. Under certain circumstances in can be reactivated.
It seems to be associated with a number of autoimmune diseases, such as multiple sclerosis, and involved in pathogenesis of some rare cancers such as Burkitt’s lymphoma, Hodgkin’s lymphoma and nasopharyngeal carcinoma. It also represents danger for people with compromised immune system such as those with HIV. It is suspected that the infection with EBV can cause long-lasting fatigue.
Like other viral infections, EBV is involved in further complications of bacterial infections such as acute otitis media, sinusitis, and pneumonia.
Close human contact is the major way of EBV transmission from host to host
Infecting usually happens via contact with saliva of infected person (that is why the disease is sometimes called “kissing disease”). EBV in saliva originates from epithelial cells of mouth and throat. The virus cannot be transferred through the air. Infection has four to six weeks incubation period. Virus is often found in the saliva of healthy people, not only those with symptoms of infectious mononucleosis.
Initial infection with EBV occurs through the virus attacking B cells of immune system and epithelial cells in tonsils. Like other herpes viruses, EBV has so-called lytic and latent phases of infection.
Lytic phase is an initial active phase of infection when virus gets multiplied. Multiple new viral particles produced at this stageare used to infect plenty of B cells in the bodydue to the absence of host immunity in the beginning of infection. Once host develops the immune response (so-called adaptive immunity), many of these B cells enter latent (dormant) stage and only occasionally get reactivated.