Topic:

Virology and viral infections (non-hiV)

Abstract No.:

ISE.445

Title:

Phylodynamics of HCV genotype 6a among injection drug users in Southern China

Author(s):

Y. Tan¹, Q. H. Wei², L. J. Chen², J. Pan², M. Q. Li², D. P. C. Chan³; ¹National Institutes of Health, Fogarty International Center, Bethesda, MD/US, ²Centre for Disease Control and Prevention, Liuzhou, Guangxi/CN, ³Stanley Ho Centre for Emerging Infectious Diseases, The Chinese University of Hong Kong, Hong Kong/CN

Abstract:

Background: An epidemic of hepatitis C virus (HCV) infection has emerged in Southern China where most infections are found among injection drug users (IDU). Molecular epidemiological and phylogenetic analyses have previously revealed a high prevalence of HCV genotype 6a in Guangxi. The present study aims to investigate the epidemic history and transmission dynamics of HCV genotype 6a in the IDU population in Guangxi, Southern China.
Methods: The study population included HCV-infected IDU attending the methadone clinic in Liuzhou, Southern China. Bayesian Markov Chain Monte Carlo analysis was performed for determining the evolutionary rate of HCV genotype 6a for E1 envelope gene and the most recent common ancestor (tMRCA) of HCV 6a, as implemented in BEAST v.1.6.2. To infer the timescale of HCV 6a expansion in Southern China, Bayesian skyline plot model was used to estimate the effective population growth over time.
Results: Between July 2006 and April 2011, a total of 190 HCV RNA-positive blood samples were collected. Of these, 79 (41.6%) were of HCV genotype 6a. The evolutionary rate of HCV 6a was estimated at 1.7 x 10^-3 substitutions per site per year (95% HPD: 6 x 10^-4, 3.2 x 10^-3) for E1. The tMRCA of this E1 lineage was dated back to 1971 and coalescent-based analysis estimated that HCV genotype 6a was introduced into Guangxi after 1970s and spread exponentially during 1990-2000.
Conclusion: The present study reconstructs the timescale of HCV 6a expansion among the IDU population in Guangxi and provides a detailed knowledge of the evolution rate and growth patterns of HCV 6a epidemic in Southern China. The exponential increase of HCV 6a infection in 1990s might have been contributed by the rapid drug trafficking between Guangxi and neighboring countries. The understanding of the evolutionary growth patterns might provide further insight of the dissemination of HCV genotype 6a among IDU in other South East Asian countries.