Surveillance and Control
Surveillance and control procedures should include:
Data on the endemicity of HEV infection have predominantly been collected in areas where outbreaks have been reported. As an exception, seroprevalence studies carried out in Egypt, where outbreaks of HEV have not been noted, showed rates of up to 60%, suggesting that most infections occurred early in life and were asymptomatic or mild.15
Outbreaks have been reported from Algeria, Bangladesh, Borneo, China, Egypt, Ethiopia, Greece, India, Indonesia, Iran, Côte d'Ivoire, Jordan, Libya, Mexico, Myanmar, Nepal, Nigeria, Pakistan, southern Russia, Somalia, eastern Sudan, and The Gambia.10, 18
Outbreaks are mainly associated with faecally contaminated drinking water; exceptions are food-borne epidemics (raw or uncooked shellfish).
HEV was first identified in India, and has since been recognized in the Middle and Far East, in northern and western Africa, the central Asian Republics of the former Soviet Union, in China and Hong Kong SAR.29
30 000 cases were reported in New Delhi, India, (1955 - 1956) after the flooding of the river Yamuna and contamination of the city's drinking water.58
20 000 cases occurred in Mandalay, Myanmar, (1976-1977) with 18% case fatality rate in infected pregnant women.10
52 000 cases were reported in Kashmir, India, in 1978.27
100 000 cases were reported in China between 1986 and 1988.48
11 000 cases occurred in Somalia, and about 4 000 cases were reported in Mexico between 1988 and 1989.
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HEV, more labile and shed in lower titres than HAV, may have disappeared from more industrialized countries in the recent past, just as HAV is currently diminishing in importance in these countries.41
Experimental immune prophylaxis against HEV based on recombinant antigens appears to confer short-term protection and may be useful for pregnant women in endemic areas and travellers coming into these regions.
At present, no commercially available vaccines exist for the prevention of hepatitis E. However, several studies for the development of an effective vaccine against hepatitis E are in progress.41, 55, 61, 62
A 55 kDa recombinant HEV-derived ORF2 protein has been used to vaccinate rhesus monkeys against different strains of hepatitis E. Although primates could still be infected, the vaccine protected them from the symptoms of disease.55, 62
The direct intramuscular injection of purified plasmid DNA containing the full-length ORF2 of HEV has induced a prolonged humoral immune response (>12 months) to the expressed structural protein ORF2 in 80% and 100% of two separate groups of challenged mice, respectively.19
Because swine HEV is immunologically cross-reactive with human HEV and their capsid genes are very conserved, swine HEV may prove useful as an attenuated vaccine for immunization against human hepatitis E through the "Jennerian" approach.33
Source: Centers of Disease Control and Prevention (CDC), Atlanta, USA:11