Hepatitis E - an introduction
Hepatitis is a general term meaning inflammation of the liver and can be caused by a variety of different viruses such as hepatitis A, B, C, D and E. Since the development of jaundice is a characteristic feature of liver disease, a correct diagnosis can only be made by testing patients' sera for the presence of specific viral antigens and/or anti-viral antibodies.48
Hepatitis E was not recognized as a distinct human disease until 1980, when specific tests for antibody against hepatitis A were first applied to the study of epidemic waterborne hepatitis in India. The results showed that the epidemics were not epidemics of hepatitis A. Actually, very few epidemics of waterborne disease in developing countries of Asia and Africa have been linked to hepatitis A.18, 40, 41
The first experimental evidence for the existence of an additional waterborne hepatitis agent was reported in 1983.40, 41 This form of non-A, non-B hepatitis came to be known as Enterically transmitted non-A non-B hepatitis (ET-NANB), Epidemic non-A non-B hepatitis (ENANB), or Faecal-oral non-A non-B hepatitis, and the agent of this disease was subsequently found to be the major cause of sporadic hepatitis cases in regions where the epidemic form was known to exist.41
Warning: hepatitis E should not be confused with hepatitis C, also called parenterally transmitted non-A non-B hepatitis (PT-NANBH), or B-like non-A non-B hepatitis.
The risk factors for HEV infection are related to resistance of HEV to environmental conditions, poor sanitation in large areas of the world, and HEV shedding in faeces.
Where is HEV a problem globally?
Hepatitis E has a restricted distribution: epidemics of hepatitis E have been found in much of Central and South-East Asia, North and West Africa, and in Mexico, confined to geographic areas where faecal contamination of drinking water is common.10
However, the application of recently developed serologic tests has revealed anti-HEV in every country in which it has been sought, including developed countries like the United States (US), in which the disease virtually does not occur.40
It is not clear whether such antibodies represent missed diagnoses of hepatitis E, asymptomatic infections, infections with attenuated strains of HEV, antibodies that cross-react with an as yet unrecognized agent, or some type of nonspecificity of the existing assays.
Possible reservoirs of HEV in the mentioned regions could be found in animals like monkeys, pigs, cows, rodents, sheep or goats. In fact, all these species are susceptible to infection with HEV.14, 18, 26, 41, 53, 54
When is a HEV infection life-threatening?
Hepatitis E is a mild to moderate disease in severity (mortality rate of 0.4-4.0%) except in pregnancy, where the mortality rate is progressively higher in each succeeding trimester and may reach 20%.
There is no hyperimmune E globulin available for pre- or postexposure prophylaxis.
HEV infections are usually self-limited, and hospitalization is generally not required. No available therapy is capable of altering the course of acute infection.