The development of molecular biology techniques has enabled us to clone the genetic sequences of three new hepatitis viruses, namely, hepatitis C virus, hepatitis E virus and hepatitis G virus (GBV-C), over the last decade.
Hepatitis C virus (HCV) is now known to account for the majority of parenterally transmitted non-A, non-B hepatitis, and hepatitis E virus (HEV) is the major cause of epidemics of enterally transmitted non-A, non-B hepatitis in less developed countries, mainly through contaminated water supplies. While 80% of those infected with HCV become chronic carriers, there is no known chronic carrier state for HEV. To date, six major genotypes of HCV have been identified, with various variants of genotype 6 described in Southeast Asia.
In Singapore, the majority of patients with chronic hepatitis C are infected with genotype 1. The seroprevalence of HEV is 10% to 14% in Singapore. This probably reflects suboptimal sanitary conditions in the past rather than a currently high HEV infection rate in the population. However, locally acquired cases of acute hepatitis E have been reported.
As for the most recently cloned hepatitis G virus, its aetiological role in the remaining cases of non-A, non-B hepatitis is still unclear. Some preliminary evidence suggests that it may be merely an innocent bystander with limited pathogenicity, and it certainly cannot account for all the remaining cases of non-A–E hepatitis. Hence, the search for yet another hepatitis virus continues.
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The author(s) declare there are no affiliations with or involvement in any organisation or entity with any financial interest in the subject matter or materials discussed in this manuscript.
