Epstein-Barr virus
Epstein-Barr virus, frequently referred to as EBV, is a member of the herpes virus family and one of the most common human viruses. The virus is present worldwide and most people become infected with EBV sometime during their lives. In general terms, as many as 95% of adults between 35 and 40 years of age have been infected. Infectious mononucleosis is the most common disease caused by EBV, leading to fever, cervical adenopathies, splenomegaly and pharyngitis. Some cases can be caused by cytomegalovirus, Toxoplasma gondii, adenovirus, etc. EBV is also in the origin of proliferative syndromes in immunosuppressed patients, as well as EBV infection is associated with Burkitt´s lymphoma and nasopharyngeal carcinoma.
Clinical features: Infants become susceptible to EBV as soon as maternal antibody protection –present at birth- disappears. Many children become infected with EBV, and these infections may cause no symptoms or be indistinguishable from other mild illnesses of childhood. In developed countries many people are not infected with EBV in their childhood years. When this infection occurs during adolescence or young adulthood, it causes infectious mononucleosis 35% to 50% of the time.
Symptoms of infectious mononucleosis are fever, sore throat and swollen lymph glands. Heart problems and involvement of the central nervous system only occurs rarely. Infectious mononucleosis is almost never fatal.
Although the symptoms of infectious mononucleosis usually resolve in 1 or 2 months, EBV remains 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 people. This reactivation usually occurs without symptoms of illness.
Diagnosis: the clinical diagnosis of infectious mononucleosis is done on the basis of the symptoms of fever, sore throat, swollen lymph glands, all lasting for 1 to 4 weeks, and the age of the patient. Usually, laboratory tests are needed for confirmation.
Antibodies to several antigen complexes may be measured for detection of Epstein-Bar virus. These antigens are the viral capsid antigen (VCA), the early antigen (EA) and the EBV nuclear antigen (EBNA). EBV diagnosis is usually carried out by three classic methods: ELISA, IFA or PCR. Different antigen titers for different antigen complexes (VCA, EA or EBNA) can help differentiate acute infection from past infection with EBV. The presence of IgM antibodies to VCA and absence of antibodies to EBNA, are indicative of primary EBV infection. An increase or high IgG antibody titers to VCA, and a lack of antibody response to EBNA after at least 4 weeks of illness, strongly suggest primary infection also. In addition, 80% of patients with active EBV infection produce antibodies to EA. The presence of antibodies to both VCA and EBNA is indicative of past infection (infections occurred 4-6 months, or even years, earlier). Since 95% of adults have been infected with EBV at some point, most adults will show antibodies to EBV, from earlier infections. High or elevated antibody levels may be present for years and are not necessarily an indicator of recent infection.
Treatment: There is no specific treatment for infectious mononucleosis other than treating the symptoms. No antiviral drugs or vaccines are available. A treatment based on steroids can be considered for those patients with severe symptoms.