HIGHLIGHTS
- HEV is an emerging zoonotic pathogen transmitted from animals to
humans.
- HEV is mainly transmitted through undercooked pig products in
developed countries.
- HEV genotypes 1 and 2 cause unprecedented waterborne epidemic and
endemic diseases in resource poor countries.
- Standardized methodology should be implemented for HEV detection in
food and environmental samples.
1 ǀ INTRODUCTION
Hepatitis E virus (HEV) infection, the cause of acute viral hepatitis
worldwide, poses a significant public health concern with high
prevalence in low-income countries. It is long-neglected although has
now also emerged as an important virus in the developed
countries.1-4 In areas with heavy seasonal rainfall,
high evaporation rates, and high population density the HEV can cause
outbreaks of acute hepatitis.5-7 According to the
World Health Organization (WHO), approximately 20 million cases of HEV
have been reported every year globally. Of the total reported cases, an
estimated 3.3 million infections are leading to asymptomatic hepatitis.
In 2015, according to the WHO estimates, approximately 44,000 deaths due
to HEV have been reported worldwide.8 HEV mortality
rate among pregnant women especially in the third trimester can reach up
to 30%.9-12
HEV is a small (approximately 27–34 nm in diameter) non-enveloped
single-stranded positive-sense RNA virus belonging to the familyHepeviridae , which consists of two genera namedOrthohepevirus (infect birds and mammals) andPiscihepevirus (infect fish). The genus Orthohepevirus is
further classified into four species known as Orthohepevirus A, B, C,
and D. Furthermore, the species Orthohepevirus A includes at least eight
distinct genotypes (HEV-1-8) infecting both humans and
animals.13-15 Genotype 1 and 2 are responsible for
large-scale water-borne epidemics in developing countries, while
genotypes 3 and 4 are responsible for small outbreaks in industrialized
countries.1,6
The species causing HEV infection in swine belongs to the Orthohepevirus
A.14 The genotype 1 and 2 are constrained to humans;
genotype 3 circulates in humans, deer, rabbits, mongooses, and swine;
genotype 4 circulates in human, pig, wild boar, cattle, cow, sheep,
goat, and yak; genotype 5 and 6 are found in wild boars; genotype 7 has
been identified in dromedary; and genotype 8 has been isolated recently
in Bactrian camels.15-17 Figure 1 demonstrates
different HEV genotypes circulate in humans and animals.