Other Hepatitis Viruses
Hepatitis A virus (HAV) is a small RNA virus that belongs to the picornavirus family. Prevalence of the virus is generally correlated with areas of poor hygiene and sanitation. Even in countries such as the United States with relatively good sanita-tion, one-third of the population has evi-dence of previous infection from hepatitis A. Although infection is acute and resolves spontaneously in the majority of these individuals, a small number of cases result in fulminant hepatitis and death.
HAV replicates in the liver and is trans-ported by bile into the stool. Transmis-sion occurs through the fecal-oral route. Two formalin-inactivated hepatitis A vac-cines are currently available in the United States. These vaccines cause formation of antibodies (seroconversion) to HAV in 94 percent of vaccine recipients after the first dose has been administered and in nearly all recipients after the second dose. In addition, immune globulin is available for individuals who require passive immuno-prophylaxis. It is generally given within two weeks after exposure to HAV or two weeks before travel to areas where HAV is endemic.
Hepatitis D (delta hepatitis) is an RNA-containing “passenger” virus that requires co-infection with HBV. Hepatitis D needs the nucleocapsid assembly function of HBV in addition to the HBsAg-derived envelope. Without these, HDV replication cannot occur. The best prevention is vac-cination against hepatitis B.
Hepatitis E virus (HEV), an RNA virus belonging to the family of caliciviruses, causes endemic and epidemic hepatitis mostly in Asia, the Middle East, North Africa, Mexico, and South America. Clini-cal illness generally occurs between the ages of 15 and 34, with a peak incidence from the age of 20 to 29. Most epidemics result from fecal contamination of water sources. Person-to-person transmission is uncommon and exposure to blood prod-ucts and intravenous drug use do not seem to increase risk. The disease is acute and often resolves spontaneously. Fulminant hepatic failure is rare with mortality at 0.1 percent to 0.6 percent. However, infec-tion in pregnancy has a mortality of 15 to 25 percent. Repeated episodes of infection are not uncommon as anti-HEV antibodies decline over time.