<FIGURE 1>
The HEV infection is prevalent in Asia and Africa.18-19 In developing countries, the HEV infection is responsible for 20-25% of acute hepatitis cases,18 and in the general population, the mortality ranges from 0.2 to 1%.15 In Africa, a high prevalence of HEV infection has been documented recently in animals with HEV genotypes closer to that of humans and some animals may act as virus reservoirs suggesting the possibility of zoonotic transmission.20 In developed countries, the HEV cases have been increased recently mainly due to the consumption of undercooked meat, and is a silent threat which need much epidemiological investigations and appropriate mitigation strategies to be adopted.18,21-22 In the present scenario, HEV is considered as an emerging zoonotic infection in many European countries.23
Autochthonous HEV causes considerable clinical problems in industrialized countries, where animal species including domestic swine, wild boar, and wild deer act as reservoirs of HEV-3 and HEV-4 genotypes. Humans acquire HEV infections by consuming uncooked or undercooked meat of the infected animals, especially pig livers or sausages made from infected livers.24 Not much data are available with regards to HEV prevalence and contamination in food as well sources of contamination, especially in developing countries, and investigations on such issues therefore would elucidate a better understanding of food-borne impact of this important virus and its maintenance.25
The disease is mainly transmitted via the fecal-oral route by ingestions of contaminated food and drinking water. HEV contamination of food sources and surface waters could occur through solid and liquid residues of infected animals, which act as zoonotic reservoirs. The food-borne transmission of HEV is mainly due to insufficiently uncooked pig products, although living in close contact with animals or irrigation water are the known risk factors of HEV infection in both healthy and immunocompromised patients.26-28 The HEV may also transmit via other routes such as zoonotic transmission, mother to child, and blood transfusion.24,29-34 The transmission of HEV from person-to-person is infrequent.34-36
The importance of HEV as an important public health issue is rising, and wide distribution of HEV in humans, animals and environmental as well as associated zoonotic concerns warrants the strengthening of One Health concept to tackle HEV. 3,23,25,28-30 This review discusses the importance of HEV infections and associated risk factors, with a particular focus on pigs, zoonotic transmissions, environmental contamination, and water-borne outbreaks.