Phylogenetic Clustering Among People With Recent Hepatitis C Virus Infection In Australia Between 2004-2015

Author: Bartlett SR, Applegate T, Jacka B, Lamoury F, Bull R, Danta M, Bradshaw D, Lloyd AR, Hellard M, Dore GJ, Matthews GV, Grebely J

Theme: Epidemiology & Public Health Research Year: 2017

Background: Little is known about hepatitis C virus (HCV) transmission among people with
recent infection and in particular among gay and bisexual men with HIV co-infection.
Phylogenetic methods can provide useful insights into transmission. The aim of this study
was to identify phylogenetic pairs and clusters among people with recent HCV infection in
Methods: Data and specimens from five studies of recent HCV in Australia recruited
between 2005 and 2015 were used for this study. Viral RNA was extracted from samples
and HCV Core-E2 region sequenced. Phylogenetic trees were inferred using maximum
likelihood analysis and 1000 bootstrap replicates. Clusters were identified using 5% genetic
distance [GD] threshold and logistic regression performed in STATA 14.1.
Results: In total, 352 participants were eligible for inclusion in this study and the proportion
with HIV/HCV co-infection was 43% (151/352). Core-E2 sequences were obtained from 237
participants. HCV genotype (GT) prevalence among sequences obtained was: GT1a/b:55%
(n=141), GT3a: 38% (n=89) and GT2/4/6: 3% (n=6). Overall, 50% of participants were in a
pair or cluster. Among HIV/HCV co-infected participants, 60% (74/123) were in a pair or
cluster, compared to 30% (34/113, p=0.013) of participants with HCV mono-infection.
Among those with GT1a, 21% (18/85) and 60% (27/45) of HCV and HIV/HCV subjects were
in a pair/cluster respectively. Clusters displayed homogeneous characteristics, such as
exclusively containing individuals from one city, with HIV/HCV co-infection, or route of
acquisition of HCV.
Conclusion: This study of recent HCV infection in Australia found a high proportion of
participants demonstrated phylogenetic clustering. Clusters’ exclusively containing
individuals with particular characteristics suggests that HCV transmission occurs through
discrete networks, particularly among HIV/HCV co-infected individuals. The greater
proportion of clustering found among HIV/HCV co-infected participants also highlights the
need to provide broad DAA access and rapid uptake, together with ongoing monitoring of the
Disclosure of Interest Statement: None to declare.

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