Etiology. Hepatitis D virus or delta virus (Hepatitis D Virus, HDV) - RNA containing a virus, the smallest of known viruses that cause human diseases. The hepatitis D virus does not have its own skin and uses the envelope of the hepatitis B virus, is a defective virus, has the ability to suppress HBsAg production. Epidemiology.The source of infection for a person is only a patient or a carrier of the virus. The main ways of transmission of the virus: parenteral, sexual. It is possible to transfer from mother to fetus together with hepatitis B virus. Infection occurs only when hepatitis B virus is infected: simultaneously with hepatitis B virus infection (coinfection) or as superinfection with chronic viral hepatitis B (HBV), in carriers of HBsAg. When co-infected with hepatitis D virus, the course of acute hepatitis B is more severe than with monoinfection (infection with HBV alone), with a higher frequency of occurrence of fulminant forms (the frequency is increased by 100 times according to some data), therefore, in cases of severe acute hepatitis B, infection should always be excluded HDV. In addition, co-infection with HDV leads to more frequent cases of chronic disease. Clinical manifestations. The disease occurs 1-6 months after infection with the virus and is accompanied by a clinic characteristic of hepatitis, often with severe course, complications, pronounced changes in transaminases. The period of the onset of convalescence is prolonged, in 4-7% of cases the chronic course develops. Diagnostics. Laboratory diagnostics is based on the detection of serological markers (immunoglobulins IgM and total antibodies) and molecular methods (detection by PCR of a virus in a qualitative format of the output of the result). Evaluation of serological markers refers to indirect methods of diagnosing infections - it allows you to assess the presence of an immune response of the body to the introduction of an agent into the body. As a screening, the determination of total antibodies is used, in the case of a positive result, the detection of antibodies of IgM class, which can be determined not only in acute hepatitis, but also in chronic. These studies are recommended for patients with viral hepatitis B and carriers of HBsAg to exclude the infection of HDV as a cause of a more severe course of hepatitis. To confirm active replication of the virus, PCR methods are used - detection of the RNA of the virus.