Table 1.

Epidemiology and clinical features of hepatitis E virus [3, 6, 10, 20, 21].

Genotype	1	2	3	4
Host	Human; also isolated from pig	Human exclusively	Human, pigs, and other mammalian species
Route of transmission	Fecal-oral; vertical transmission; zoonotic (genotype 1)		Zoonotic (usually swine, with humans being accidental hosts); environmental (shellfish, river); blood transfusion
Geographical distribution	Mainly Asia and Latin America (Cuba, Venezuela, and Uruguay)	Mexico and West Africa	Worldwide	China, East Asia, Central Europe, and America
Epidemiological features	Causes epidemic outbreaks and sporadic cases in developing countries; occasionally in travelers returning from developing countries	Causes epidemic outbreaks and sporadic cases in developing countries	Causes sporadic autochthonous cases in developed countries
Seasonality	Yes (outbreaks in flooding/monsoon)		No
Clinical presentation	Mostly asymptomatic; acute self-limited hepatitis	Mostly asymptomatic; acute self-limited hepatitis	Varies from asymptomatic to acute self-limited hepatitis and may lead to chronicity in immunosuppressed cases (HEV3)
Age	Adolescents and young (15–30 y)		Middle-aged and elderly (>50 y)
Gender (M : F)	2 : 1		>3 : 1
Prognosis	High mortality in pregnancy and in patients with underlying chronic liver disease	Fulminant hepatitis has not been noted in HEV2	Higher overall mortality rate relative to genotype 1; higher mortality among older adults
Chronic infection	No		Yes	Yes