Hepatitis E

Hepatitis E is inflammation of the liver caused by infection with the hepatitis E virus (HEV); it is a type of viral hepatitis. Hepatitis E has mainly a fecal-oral transmission route that is similar to hepatitis A, although the viruses are unrelated. HEV is a positive-sense, single-stranded, nonenveloped, RNA icosahedral virus and one of five known human hepatitis viruses: A, B, C, D, and E. Like hepatitis A, hepatitis E usually follows an acute and self-limiting course of illness (the condition is temporary and the individual recovers) with low death rates in resource-rich areas; however, it can be more severe in pregnant women and people with a weakened immune system, with substantially higher death rates. In pregnant women, especially in the third trimester, the disease is more often severe and is associated with a clinical syndrome called fulminant liver failure, with death rates around 20%. Whereas pregnant women may have a rapid and severe course, organ transplant recipients who receive medications to weaken the immune system and prevent organ rejection can develop a slower and more persistent form called chronic hepatitis E, which is so diagnosed after 3 months of continuous viremia. HEV can be clustered genetically into 8 genotypes, and genotypes 3 and 4 tend to be the ones that cause chronic hepatitis in the immunosuppressed. In 2017, hepatitis E was estimated to affect more than 19 million people. Those most commonly at risk of HEV are men aged 15 to 35 years of age. A preventive vaccine (HEV 239) is approved for use in China. The virus was discovered in 1983 by researchers investigating an outbreak of unexplained hepatitis among Soviet soldiers serving in Afghanistan. The Russian virologist Mikhail S. Balayan discovered the virus after he ingested fecal samples of 9 soldiers mixed with kefir. The earliest well-documented...