Viral hepatitis type D is an acute and chronic liver inflammatory disease caused by hepatitis D virus (HDV) and hepatitis B virus and other hepatotropic DNA viruses. HDV is a defective virus, and it is rare to be infected with HDV alone. It can only exist in people infected with HBV and certain animals with positive surface antigen of hepatotropic DNA virus. The clinical manifestations of hepatitis D depend to a certain extent on the status of concurrent HBV infection. Over-infection of HDV and HBV can aggravate liver damage and easily develop into chronic active hepatitis, cirrhosis and severe hepatitis. Hepatitis D is mainly transmitted through blood transfusion and blood products, which is similar to the transmission mode of hepatitis B.