HEPATITIS-E VIRUS - A REVIEW

Hepatitis E, a faecal-oral waterborne acute viral hepatitis, occurs mo st frequently in epidemic outbreaks in developing countries. Hepatitis E virus (HEV) is spherical, nonenveloped and varied in size from 27 t o 34 nm with a spiked surface. Experimental HEV infection in primates, molecular cloning involving cDNA libraries and recombinant protein te chnology indicate that the genome can be assigned to a 7.6 kb single s tranded positive polyadenylated RNA. In a 5'NS-S poly A 3' molecular s tructure, three partially overlapping ORF have been identified. Two st rains (Burma and Mexico) have been studied and although they related t o caliciviruses, the genetic organization indicates that it represents different agents ranged in a new subgroup: the alpha-like viruses. HE V is an important cause of morbidity and mortality in developing count ries in the 15 to 40 year age-group and although the mortality rate is low in the general population (0.5 to 3%), it averages 17 to 20% amon g third-trimester pregnant women. Several sporadic cases have been rec ently identified among children. The prevalence of anti-HEV antibodies in blood donors ranges from 2 to 3% in North Europe and USA and from 6.8% in Spain to 70% in Thailand The average incubation period is 6 we eks. Chronic liver disease, persistent viraemia and oncogenicity have not been observed. HEV particles are identified in stool or bile by im mune electron microscopy, capture immunoassay or RT-PCR. After 9 fluor escent antibody blocking assay using sections from infected livers, El isa and Western blotting with recombinant, synthetic or fusion protein s corresponding to the major ORF epitopes have been used to investigat e IgM and IgG HEV anti-bodies in 94% of cases. Cell culture is current ly unable to produce the amounts of antigen required for the developme nt of virus vaccines but fusion proteins might be a suitable candidate vaccine for hepatitis E. At the present time the only effective measu res for prevention of hepatitis E are improved sanitation and water ha ndling.