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 presentation of icterus or jaundice is a characteristic symptom of liver disease, a specific diagnosis of infection by a hepatitis virus can only be made by testing patients' sera for the presence of specific viral antigens, nucleic acid sequences and/or anti-viral antibodies.
Hepatitis E was not recognized as a significant 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 due to hepatitis A; indeed, very few epidemics of waterborne disease in developing countries of Asia and Africa have been linked to hepatitis A.
The first experimental evidence for the existence of an additional waterborne hepatitis agent was reported in 1983. 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 disease was known to appear.
 Balayan MS, et al. (1983) Evidence for a virus in non-A, non-B hepatitis transmitted via the fecal-oral route. Intervirology 20:23-31.