Acute Viral Hepatitis

Acute viral hepatitis refers to hepatic infection by the hepatotropic viruses hepatitis A–E. The acute infections look similar with regard to histologic features, with spotty necrosis throughout the lobules, hepatocyte unrest, swelling and apoptosis, and portal tract and intrasinusoidal inflammation, chiefly lymphocytes. The differential diagnosis histologically includes drug-induced liver injury. Structural differences and epidemiology define the major differences in the course of each of these viral infections. Hepatitis A and E are similar in causing only acute hepatitis, while some cases of hepatitis B and many of hepatitis C become chronic. The prevalence of hepatitis D virus (HDV) infection has seen a reduction worldwide due to hepatitis B vaccination programs. Nonetheless, major cities with continued intravenous drug use remain reservoirs with a rate of approximately 8% in Europe. The availability of direct-acting viral agents is spearheading efforts by WHO to eliminate new and chronic HCV infections by 2019. Histologic cholestasis may be a particular feature of acute hepatitis E. It should be noted that hepatitis E virus has four major genotypes of which 1 and 2 infect humans (resulting in travel/endemic-related hepatitis with cholestasis and high mortality in pregnant women) and 3 and 4 are zoonotic and infect pigs, boar and several other animal and avian species (and may cause hepatitis associated with poorly or uncooked meat).