Hepatitis E virus - Introduction, Classification, Morphology, Genome, Epidemiology

Classification of Hepatitis E virus

The classification of Hepatitis E virus is as follows:

Family: Hepeviridae

Genus: Orthohepevirus

Species: Hepacivirus E

Hepatitis E virus is the primary cause of enterically transmitted non-A non-B hepatitis virus (NANBH). All Hepacivirus E viruses that infect humans belong to Orthohepevirus A and consist of at least 8 distinct genotypes.

• Genotype 1 HEV (mostly Asian isolates)

• Genotype 2 HEV (a Mexican isolate and some African isolates infects only human)

• Genotypes 3 (infects humans, pigs, rabbits, deer, mongoose)

• Genotypes 4 (infects humans, pigs, rabbits, deer, mongoose)

• Genotypes 5 and 6 HEVs infect wild boars

• Genotype 7 HEV infects dromedary camels and reportedly a human

• Genotype 8 HEV infects Bactrian camel

Morphology of Hepatitis E virus

Morphologically, the Hepatitis E virus is non-enveloped, spherical, and 32-34 nm in diameter. It is positive single-stranded RNA which is 7.6 kb in size. The genome enclosed within a capsid is composed of 60 capsid proteins.

Genome of Hepatitis E virus

Hepatitis E virus genome contains 3 ORF:

• ORF 1 => largest, codes for NSP responsible for viral replication

• ORF 2 => encodes for the capsid (660 amino acid)

• ORF 3 => virion morphogenesis and release

It has only 1 serotype.

Epidemiology of Hepatitis E virus

Hepacivirus E infects 1/3 of the world's population through exposure.

• Genotype 1: Asia, Africa

• Genotype 2: Mexico, Africa

• Genotype 3: Western countries

• Genotype 4: Asia, Europe

There are two distinct clinical-epidemiological patterns of Hepatitis E virus.

In areas of poor sanitation, HEV1 and HEV 2 are transmitted between humans by the fecal-oral route, usually via contaminated water. This results in frequent sporadic cases and occasional large outbreaks. (excess mortality in pregnant women).

In developed countries, HEV3 and HEV4 are sporadically transmitted zoonotically from animal reservoirs through the consumption of undercooked pork or meat, or shellfish.

(elderly males are at higher risk, and HEV3 may cause chronic infection).

How is HEV inactivated?

• the virus remains viable after heating for 1 hour at 56°C

• The cooking temperature at 71°C for 20 minutes is required to fully inactivate the virus

Host: Human, Pig, Monkey, Some rodents, and chicken