Hepatitis E virus in the Western world--a pork-related zoonosis

Hepatitis E virus (HEV) is a common cause of waterborne epidemics of acute hepatitis worldwide, but its natural history, ecology, clinical significance and presentation are entirely different in the developed world, where, apart from the typical travel-associated imported cases, the majority of the observed cases involve older adults with comorbidities or forms of immune compromise who acquire HEV genotype 3, mostly through direct or indirect (consumption of meat products) contact with pigs. Thus, HEV is zoonotic in the developed world, a fact that has been recently recognized, and is of major importance in medical, veterinary and public health terms. The present article evaluates the current knowledge about the zoonotic nature of HEV in the industrialized world, outlines the numerous questions that still exist regarding the role of pigs in viral ecology, summarizes knowledge about clinical disease in its zoonotic form, and discusses where future scientific efforts should focus.