Identification of a novel strain of hepatitis E virus responsible for sporadic acute hepatitis in Taiwan.

Hepatitis caused by the hepatitis E virus (HEV) is a self-limited disease and occurs most frequently as epidemic or sporadic hepatitis in developing countries. The role of HEV in sporadic acute hepatitis in areas without a history of hepatitis E epidemics is obscure. Recently, it was found that more than 10% of the patients with acute non-A, non-B, non-C hepatitis in Taiwan were associated with an acute HEV infection. Nucleotide sequences of the regions within the first open reading frame of HEV were determined in four cases and were 96.7-100% identical to each other. As compared to the isolates from China, Pakistan, Burma, India, Africa, and Mexico, the similarities were, however, only 71.7-79.3%. Phylogenetic analysis revealed that the four Taiwan isolates were categorized as a novel HEV group (the Taiwan strain), which was distinct from all of the strains isolated from other parts of the world. In addition, the isolates from China, Burma, India, and Pakistan were catalogued as the second genotype of HEV (the Asian strain), and the Mexican isolate as the third (the Mexican strain). The African isolate was more related to the Asian type and might be a subtype of the Asian strain. A simple genotyping method by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) is described. The findings also support the hypothesis that HEV may be responsible for some sporadic acute non-A, non-B, non-C hepatitis in other developed countries.