The presence of overlapping infection of HCV and HBV affects the prognosis of liver disease HCV infection in patients with chronic liver disease, especially dual infection of HBV and HCV, may accelerate the progression of liver disease. Viral hepatitis (viralhepatitis) is a group of infectious diseases caused by a variety of different hepatitis viruses, mainly liver damage, according to the pathogenic diagnosis, there are at least five types of hepatitis viruses, namely hepatitis A, B, C, D and E viruses, which cause viral hepatitis A, B, C, D and E, respectively, namely hepatitis A (hepatitis A), hepatitis B ( hepatitis B), hepatitis C), hepatitis D) and hepatitis E). Another type of viral hepatitis, called hepatitis G, is less common. The strength of the immune response and the normal function of immune regulation are closely related to the clinical type of hepatitis B and its regression. In an organism with normal immune response and immunoregulatory function, the infected hepatocytes are destroyed by effector cell attack, and the infection is terminated, and the clinical manifestation is a smooth acute hepatitis with or without acute jaundice, depending on the amount of virus and the degree of hepatocyte damage due to virulence. If the body’s specific humoral and cellular immune function against HBV is severely deficient or immune tolerance or immune paralysis, the infected hepatocytes do not suffer from immune damage or only minor damage, and the virus is not cleared, then the patient will show asymptomatic chronic carriers. If the body’s immune function (mainly clearance function) is low, the virus is not completely cleared, and the liver cells are constantly and mildly damaged, then it manifests as chronic migratory hepatitis, chronic active hepatitis. The pathogenesis of chronic active hepatitis is complicated by the fact that the body cannot adequately clear the virus from the circulation and the infected hepatocytes due to low specific immune function, and the virus continues to replicate in the hepatocytes, causing continuous immune damage to the hepatocytes, and the immune regulatory molecules formed in the liver are qualitatively and quantitatively altered due to insufficient number or function of suppressor T cells and metabolic malfunction of the hepatocytes, resulting in immune regulatory The dysfunction of immune regulation, resulting in malfunction of coordination between T-B cells and T cell subsets, increased autoantibody production, and autoimmune liver injury through antibody-dependent cytotoxic effects or antibody-mediated complement-dependent cytolytic effects; or the formation of a large number of antigen-antibody complexes, resulting in more serious and lasting damage to hepatocytes and other organs. The mechanism of damage in the pathology of severe hepatitis is mainly due to severe dysfunction of the body’s immune function, enhanced specific immune response, and marked autoimmune response, causing massive necrosis of hepatocytes through intrahepatic immune complex reactions and antibody-dependent cytotoxic effects. In recent years, it is believed that the massive release of tumor necrosis factor-α (TNFα) due to endotoxemia causes local microcirculatory disorders, which can lead to acute hemorrhagic necrosis and massive necrosis in the liver; and free radical changes have been found to be related to the occurrence of liver injury and hepatic encephalopathy. Little is known about the pathogenesis of hepatitis C and E. Some studies suggest that the immune system is involved in the pathogenesis of hepatitis C and E, and that hepatocellular injury is mainly immune-mediated. Animal studies on hepatitis D have shown that overlapping HDV and HBV infections lead to significant HDV replication, significantly more than HDV and HBV co-infections. HDV is directly pathogenic to hepatocytes, and hepatocellular damage is significantly increased in hepatitis B with HDV infection, especially in those with overlapping infections. There is no cross-immunity between viral hepatitis types. HDV and HBV co-infection or overlapping infection can aggravate the disease and predispose to chronic hepatitis and severe hepatitis, especially HDV overlapping infection in chronic hepatitis B. HAV or HBV overlapping infection also aggravates the disease and can even develop into severe hepatitis.