Infectious erythema

Infectious erythema is a disease caused by parvovirus B19( B19U).This infection is also called the "fifth disease" in addition to the four well-known TORCH infections( toxoplasma, others, rubella, cytomegalovirus, herpes simplex - toxoplasma infection, rubella, CMV infection, herpetic infection).Depending on the age of the patient, infectious erythema is characterized by various symptoms: from erythematous rash and fever to severe forms of arthritis and lymphadenopathy. Infection is transmitted by airborne droplets( the incubation period is about 7 days), but infection can occur with blood transfusions or through the placenta from pregnant to the fetus. Most often, children 4-11 years old fall ill, in adults infectious erythema is very difficult( especially in women older than 30 years).In pregnant women, viral infection in the I and II trimesters of pregnancy causes fetal hydrops( in 5-10% of cases) and leads to miscarriages and intrauterine

fetal death( in 9-13% of cases).The greatest risk of developing these complications occurs with infection between the 10th and 26th weeks of pregnancy.

Parvovirus B19 is a single-stranded DNA-containing virus with a diameter of 18-24 nm, which does not have a membrane. When human infection with the receptor for parvovirus B19 is P-Ar, which is expressed on erythrocytes, erythrocarytes, megakaryocytes, endothelial cells, placenta cells, liver and fetal heart. Organs and tissues containing cells with P-receptor, become a target for parvovirus, which largely determines the specificity of clinical manifestations of infection. The frequency of P-Ag among the indigenous inhabitants of Europe is 70-80%.Parvovirus B19 replication occurs in erythrocarytes of the bone marrow for 21 days. In the absence of P-Arg, the virus does not infect and replicate.

In all cases of infection with parvovirus B19, partial red cell aplasia of the bone marrow develops. Aplasia of the bone marrow leads to a decrease in the number of erythrocytes and the concentration of Hb in the blood, reticulocytopenia and anemia, the severity of which depends on the degree of aplasia. Usually hematological blood counts are normalized within 10 days after the disappearance of fever, in some cases signs of anemia can persist up to 4 weeks. The number of platelets, lymphocytes and granulocytes also decreases. In the future, anemia is fully compensated for by the formation of new red blood cells. After the transferred infection the stable lifelong immunity caused by АТ of class IgG is formed. In individuals with immunodeficiency, regardless of its cause, the persistence of the virus( the constant presence of DNA of the virus in tissues or blood) is most often noted, since the synthesis of AT to the B19 virus is violated.

For the diagnosis of parvovirus infection, the Ig classes of IgM and IgG in serum are determined by ELISA.