HDV is a hepatitis D virus, a defective single-stranded complex-stranded RNA virus that must rely on hepatitis B virus and other hepatophilic DNA viruses to provide a shell for its replication. The HDV is easily mutated and can significantly inhibit the synthesis of HBV-DNA after infection with the hepatitis D virus.3. Transmission route: HDV is mainly transmitted through blood transfusions and blood products, similar to the transmission of hepatitis B virus.4. Infected population: HDV is mostly seen in people infected with hepatitis B virus, but can also be seen in people with sporadic acute hepatitis virus infection.5. Adverse effects 5, adverse effects: HDV and hepatitis B virus overlap infection, can contribute to increased liver damage, and easy to develop chronic active hepatitis, cirrhosis, heavy hepatitis.