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The origin of Hepatitis C virus genotypes
For many RNA viruses, relatively recent times of origin of extant viruses are
implied by the high rate of substitution observed in longitudinal studies. However,
extrapolation of short-term rates of substitution can give misleading estimates
of times of divergence.
We show here that the common ancestor of different types of Hepatitis C virus
(HCV) is older than previously thought. The rate of HCV sequence change was
measured amongst a cohort of individuals infected following administration of
anti-D immunoglobulin. Virus sequences were obtained in the E1 and NS5B genes
and compared with each other and with sequences from an infective batch. Taking
account of the bias towards synonymous transition substitutions, the time of
divergence of variants of subtype 1b is estimated to have occurred 70-80
years ago. The numerous subtypes of HCV are proposed to derive from more
than 300 years of endemic infection in certain geographical regions, with recent
spread of some subtypes to other parts of the world. Estimation of the time
of origin of the major HCV genotypes (types 1-6) is problematic, but our data
and analogy with other viruses suggest that divergence occurred at least
500-2000 years ago.
Author: Smith DB, Pathirana S, Davidson F, Lawlor E, Power J, Yap PL, Simmonds
P, Department of Medical Microbiology, University of Edinburgh, Medical School,
UK. dbs@srv1.med.ed.ac.uk
Source: J Gen Virol 78: 321-328 (1997)
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