Hepatitis E 

Hepatitis E is an enterically transmitted infection that is typically self-limited.^{[1, 2]} It is caused by the hepatitis E virus (HEV) and is spread by fecally contaminated water within endemic areas.^{[3, 4, 5]} Outbreaks can be epidemic and individual. Hepatitis E has many similarities with hepatitis A. Hepatitis E has been associated with chronic hepatitis in solid organ-transplant recipients.^[6]

The course of infection has 2 phases, the prodromal phase and the icteric phase. The infection is self-limited. Whether protective immunoglobulins develop against future reinfection remains unknown. The overall case fatality rate is 4%, though pregnant women and liver transplant recipients may be at substantially higher risk.

Therapy should be predominantly preventive, relying on clean drinking water, good sanitation, and proper personal hygiene. A successful recombinant hepatitis E vaccine has been developed.^{[7, 8]}

The HEV genome contains 3 open reading frames (ORFs). The largest, ORF-1, codes for the nonstructural proteins responsible for viral replication. ORF-2 contains genes encoding the capsid. The function of ORF-3 is unknown, but the antibodies directed against ORF-3 epitopes have been identified.

Hepatitis E results from HEV infection and is spread by fecally contaminated water within endemic areas. HEV is an RNA virus of the genus Hepevirus. It was discovered during electron microscopy of feces contaminated with enteric non-A, non-B hepatitis. The virus is icosahedral and nonenveloped. It has a diameter of approximately 34 nanometers, and it contains a single strand of RNA approximately 7.5 kilobases in length. Four HEV genotypes exist, and genotype 1 causes human disease.

United States statistics

The prevalence rate of anti-HEV antibodies in the United States is less than 2%. The route of exposure is unknown but is generally attributed to travel in endemic areas.

International statistics

Hepatitis E has worldwide distribution, but predominating factors include tropical climates, inadequate sanitation, and poor personal hygiene. It is found most often in developing countries near the equator, in both the Eastern and Western hemispheres. Outbreaks are associated with rainy seasons, floods, and overcrowding.

Water supply contamination with human feces is a frequent source of epidemics. The largest outbreak was reported in northeast China, with 100,000 people affected between 1986 and 1988. The reservoir of HEV is unknown, but it is believed that the virus may be transmitted by animals.

Age-, sex-, and race-related demographics

Hepatitis E predominantly affects persons aged 15-40 years. It may affect younger age groups, but it generally is not recognized and may be subclinical in these populations. No chronic cases have been described. Although hepatitis E is not known to have a predilection for either sex, pregnant women are prone to complications. Hepatitis E has no apparent racial predilection.

No chronic cases of acute hepatitis E have been reported. The infection is self-limited. Whether protective immunoglobulins develop against future reinfection remains unknown. The overall case fatality rate is 4%.

Among pregnant women, the case fatality rate is 20%, and this rate increases during the second and third trimesters. Reported causes of death include encephalopathy and disseminated intravascular coagulation. The rate of fulminant hepatic failure in infected pregnant women is high.

Liver transplant recipients may be at a greater risk for HEV infection, which can lead to chronic hepatitis.^[9] However, if the patient has antibodies against HEV, the risk of reactivation is extremely low. When a suitable vaccine becomes available, patients on a transplant waiting list may be vaccinated to help avoid reactivation of the HEV.