For professionals:

• HEV virus is a spherical, non-enveloped, single stranded RNA virus approximately 32 to 34 nm in diameter. HEV has been provisionally classified in the Caliciviridae family; however, the organization of the HEV genome is substantially different from that of other caliciviruses and HEV may eventually be classified in a separate family.

• Enterally transmitted non-A, non-B hepatitis.

• Outbreaks occur primarily in countries with poor environmental sanitation.

• Outbreaks usually occur as water-born epidemics.

• Unlike hepatitis A virus, person-to-person transmission of HEV appears to be uncommon. However, nosocomial transmission, presumably by person-to-person contact, has been reported to occur.

• U.S. cases usually have history of travel to HEV-endemic areas

• Outbreaks identified in Myanmar(Burma), India, Bangladesh, Nepal, Central Asian republics of the former Soviet Union, Mexico, China.

• Incubation period: 15~60 dyas (Average 40 days).

• The infection rate is highest in young adults (15 ~ 40 yrs old), and uncommon in children and the elderly. (HAV, mostly infect children)

• The virus has two main geographically distinct strains, Asian and Mexican; recently, several novel isolates from nonendemic areas and genetically related swine HEV and rodnets have been reported.

• Its overall case-fatality rate is 1%~3%. In pregnant women, severe symptoms with case-fatality rate as high as 20 %.

• Self-limiting infection without chronicity.

• Subclinical infection may occur.

• Animals and subclinical human infection may be reservoirs of HEV.

• In two human volunteer studies:
  • Liver enzyme elevations occurred 4-5 weeks after oral ingestion and persisted for 20-90 days
  • Virus excretion in stools occurred approximately 4 weeks after oral ingestion and persisted for about 2 weeks.
  • The titer of IgM anti-HEV declines rapidly during early convalescence; IgG anti-HEV persists and appears to provide at least short-term protection against disease.
  • Several diagnostic tests are available in research laboratories, including enzyme immunoassays and Western blot assays to detect IgM and IgG anti-HEV in serum, polymerase chain reaction tests to detect HEV RNA in serum and stool, and immunofluorescent antibody blocking assays to detect antibody to HEV antigen in serum and liver.

• The swine and human HEV strains from Taiwan formed a monophyletic group, distinct from three previously reported groups: the United States human and swine HEV strains, the Mexico strain, and the largest group composed of the Asian and the African strains. The identity of nucleotide sequences was 84-95% between swine and human HEV strains in Taiwan, and 72-79% between Taiwan strains and those from different areas. The predicted amino acid sequence of a Taiwan swine HEV strain within the peptide 3-2 used in commercial anti-HEV assay showed a high identity (91-94%) with those of other human and swine HEV strains. (Clinical and epidemiological implications of swine hepatitis E virus infection.--Wu JC, Chen CM, Chiang TY, Sheen IJ, Chen JY, Tsai WH, Huang YH, Lee SD. -- Institute of Clinical Medicine and Division of Gastroenterology, Veterans General Hospital, National Yang-Ming University School of Medicine, Taipei, Taiwan.--J Med Virol 2000 Feb;60(2):166-71)
• Swine may be a reservoir of HEV and subclinical swine HEV infection may occur. Cross-reactivity of current anti-HEV assay may account for the high prevalence rate of anti-HEV in the general population in nonendemic areas.

• Prevention:
  • Avoiding drinking water (and beverages with ice) of unknown purity, uncooked shellfish, and uncooked fruits or vegetables that are not peeled or prepared by the traveler.
  • No products are available to prevent hepatitis E at present.
  • IG prepared from plasma collected in non-HEV-endemic areas is not effective in preventing clinical disease during hepatitis E outbreaks and the efficacy of IG prepared from plasma collected in HEV-endemic areas is unclear.