Data for this Review were identified by searches of Medline, Current Contents, and references from relevant articles; several articles were identified through searches of the extensive files of the authors. Search terms used were “hepatitis E”, “HEV in animals”, “HEV transmission”, “HEV genotypes”, and “HEV serology”. No language or date restrictions were set in these searches.
ReviewHepatitis E: an emerging infection in developed countries
Introduction
Hepatitis E is an important public-health concern as a major cause of enterically transmitted hepatitis worldwide, and is responsible for over 50% of cases of acute viral hepatitis in endemic countries.1, 2 The virus is transmitted primarily by the faecal–oral route and is associated with both sporadic infections and epidemics in areas with poor sanitation and weak public-health infrastructures. In developed countries, hepatitis E infections were traditionally thought to occur infrequently and only in individuals who had become infected while travelling in an area where the virus is endemic.3 However, cases of sporadic hepatitis E in people with no history of recent travel have been reported in developed regions such as North America, Europe, Japan, New Zealand, and Australia.4, 5, 6, 7, 8, 9, 10, 11, 12 The reporting of such infections together with the availability of more comprehensive molecular and serological data has led to the re-evaluation of hepatitis E virus (HEV) epidemiology, and the acceptance that autochthonous (locally acquired) hepatitis E is a clinical problem in developed countries.
Section snippets
The HEV virus
HEV is a single-stranded, positive-sense RNA virus and the sole member of the genus Hepevirus. Two major species of the virus are recognised: mammalian HEV, a virus that causes acute hepatitis in human beings and has a reservoir in pigs and possibly a range of other mammals; and avian HEV, causing big liver and spleen disease in chickens.13 This Review focuses on mammalian HEV, since avian HEV differs genetically from mammalian HEV, has never been recovered from mammals, and has not been
HEV in developing countries
HEV was not recognised as a distinct aetiological agent until the 1980s; until then, epidemics of hepatitis in the developing world had been linked to hepatitis A virus (HAV) infections.25, 26 The subsequent development of serological assays showed HEV to be endemic throughout tropical and subtropical countries, with periodic epidemics reported from the Indian subcontinent,27, 28, 29, 30 southeast Asia,31, 32 Africa,33, 34, 35 and Mexico.36 Although foodborne epidemics have been reported in
Clinical and laboratory features
The clinical features of autochthonous hepatitis E infection range from asymptomatic infection to mild hepatitis to subacute liver failure.4, 5, 6, 7, 8, 9, 10, 11, 12, 52 In a UK hospital-based study of patients with unexplained hepatitis, 40 patients with autochthonous hepatitis E were identified, of whom 75% were icteric, with affected individuals presenting a range of other non-specific symptoms (table 1).52
The incubation period of autochthonous hepatitis E infection ranges from 2 to 9
Conclusions
Hepatitis E in developed regions is far more common than previously recognised and could have a zoonotic source. The disease has a predilection for older men in whom it carries a substantial morbidity and mortality, particularly in patients with chronic liver disease. Hepatitis E should be included in the differential diagnosis in patients with unexplained hepatitis, whatever their age or travel history. The incidence of autochthonous hepatitis E in developed countries is unknown, as is the
Search strategy and selection criteria
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