70 Unlike many other enterically-transmitted

infections, person-to-person buy MG-132 transmission of HEV appears to be uncommon.71,72 Thus, secondary attack rates among household contacts of patients with hepatitis E are only 0.7% to 2.2%, as compared to 50% to 75% for hepatitis A. Even when multiple cases occur in a family, the time interval between cases is usually short, indicating a shared primary water-borne infection rather than person-to-person spread.71 Materno-fetal73 and transfusion-related transmission74 of HEV are well documented. However, the contribution of these routes to the overall disease burden appears to be small. In the US, Europe (including UK, France, the Netherlands, Austria, Spain and Greece), and developed countries of Asia-Pacific

(Japan, Taiwan, Hong Kong, Australia), hepatitis E is responsible for only occasional cases with acute viral hepatitis. Initially, most such cases were found to be related to travel to high-endemic areas. However, in recent years, solitary cases or small case series related to autochthonous (locally-acquired) hepatitis E in these regions have been reported.25–27 In the UK, a seasonal variation with peaks in spring learn more and summer has been reported.75 These rare autochthonous cases of hepatitis E in these areas are believed to be caused by zoonotic spread of infection from wild or domestic animals,75,76 since HEV isolates from them are genetically related to swine isolates.25–27 Experimental cross-species transmission of human isolates to pigs, and of swine HEV to primates supports this view.27,57 A cluster of Japanese cases among persons who had consumed inadequately-cooked deer meat a few weeks prior to the onset of illness has been reported.51 The genomic sequences of HEV isolated from these cases were identical to those from the left-over frozen meat, establishing food-borne transmission; these isolates also had a high (99.7%)

genomic sequence homology with those from a wild boar and another Oxymatrine wild deer from the forest where the implicated deer had been hunted, suggesting transmission between wild boars and deer.77 A proportion of commercial packets of pig liver sold in Japanese and US grocery stores have been shown to contain genotype 3 or 4 HEV.78,79 This finding, along with the reported association of sporadic hepatitis E cases with eating uncooked or undercooked pig livers in case-control studies, suggests that at least some autochthonous cases are related to consumption of contaminated meat. Contaminated shellfish has also been proposed as a potential vehicle. The reservoir of HEV responsible for maintaining the disease in hyperendemic populations has not been clearly determined. Protracted viremia and prolonged fecal shedding of HEV have been suggested; however, we found that viral shedding in feces lasts for only a short period.