The hepatitis E virus (HEV) is a common cause of hepatitis that is transmitted via the intestinal tract, and is not caused by the hepatitis A virus. Spread most often by contaminated drinking water, HEV infection occurs mainly in developing countries.
Hepatitis E is also known as epidemic non-A, non-B hepatitis. Like hepatitis A, it is an acute and short-lived illness that can sometimes cause liver failure. HEV, discovered in 1987, is spread by the fecal-oral route. It is constantly present (endemic) in countries where human waste is allowed to get into drinking water without first being purified. Large outbreaks (epidemics) have occurred in Asian and South American countries where there is poor sanitation. In the United States and Canada no outbreaks have been reported, but persons traveling to an endemic region may return with HEV.
Causes and symptoms
There are at least two strains of HEV, one found in Asia and another in Mexico. The virus may start dividing in the gastrointestinal tract, but it grows mostly in the liver. After an incubation period (the time from when a person is first infected by a virus until the appearance of the earliest symptoms) of two to eight weeks, infected persons develop fever, may feel nauseous, lose their appetite, and often have discomfort or actual pain in the right upper part of the abdomen where the liver is located. Some develop yellowing of the skin and the whites of the eyes (jaundice ). Most often the illness is mild and disappears within a few weeks with no lasting effects. Children younger than 14 years and persons over age 50 seldom have jaundice or show other clinical signs of hepatitis.
Hepatitis E never becomes a chronic (long-lasting) illness, but on rare occasions the acute illness damages and destroys so many liver cells that the liver can no longer function. This is called fulminant liver failure, and may cause death. Pregnant women are at much higher risk of dying from fulminant liver failure; this increased risk is not true of any other type of viral hepatitis. The great majority of patients who recover from acute infection do not continue to carry HEV and cannot pass on the infection to others.
HEV can be found by microscopically examining a stool sample, but this is not a reliable test, as the virus often dies when stored for a short time. Like other hepatitis viruses, HEV stimulates the body's immune system to produce a substance called an antibody, which can swallow up and destroy the virus. Blood tests can determine elevated antibody levels, which indicate the presence of HEV virus in the body. Unfortunately, such antibody blood tests are not widely available.
There is no way of effectively treating the symptoms of any acute hepatitis, including hepatitis E. During acute infection, a patient should take a balanced diet and rest in bed as needed.
In the United States hepatitis E is not a fatal illness, but elsewhere about 1-2% of those infected die of advanced liver failure. In pregnant women the death rate is as high as 20%. It is not clear whether having hepatitis E once guarantees against future HEV infection.
Most attempts to use blood serum containing HEV antibody to prevent hepatitis in those exposed to HEV have failed. Hopefully, this approach can be made to work so that pregnant women living in endemic areas can be protected. No vaccine is available, though several are being tested. It also is possible that effective anti-viral drugs will be found. The best ways to prevent hepatitis E are to provide safe drinking water and take precautions to use sterilized water and beverages when traveling.
Antibody— A substance made by the body's immune system in response to an invading virus, the antibodies then attack and destroy the virus.
Incubation period— The time from when a person is first infected by a virus until the appearance of the earliest symptoms.
Jaundice— Yellowing of the skin that occurs when pigments normally eliminated by the liver collect in high amounts in the blood.
Sanitation— The process of keeping drinking water, foods, or any anything else with which people come into contact free of microorganisms such as viruses.
Vaccine— A substance prepared from a weakened or killed virus which, when injected, stimulates the immune system to produce antibodies that can prevent infection by the natural virus.
American Liver Foundation. 1425 Pompton Ave., Cedar Grove, NJ 07009. (800) 223-0179. 〈http://www.liverfoundation.org〉.
King, J. W. Bug Bytes. Louisiana State University Medical Center. 〈http://www.ccm.lsumc.edu/bugbytes〉.