The social and genetic epidemiology of Hepatitis C in an isolated network of people who inject drugs

Abstract

Background and Aims

Hepatitis C (HCV) causes liver cirrhosis, liver cancer and is a leading cause of death worldwide. In the UK the commonest risk factor for HCV is current or previous injecting drug use but many cases are undiagnosed and many known cases are disengaged from treatment services. The Isle of Wight (IOW) is a deprived, rural and geographically isolated population but suffers from the same obstacles to HCV care as larger nearby mainland populations.
The overall aim of this thesis is to understand the burden of HCV in people who inject drugs (PWID) on the IOW and how their social network could be utilised in an HCV elimination strategy.

Method

A sequential mixed method research design was used. Qualitative methods informed the design of a quantitative survey, which recruited PWID via respondent driven sampling (RDS) for a social network questionnaire and HCV bio-behavioural survey. This was used to estimate the population prevalence of HCV and the total population size of PWID on the IOW. Data from the social network survey were combined with a phylogenetic analysis of HCV RNA positive cases and qualitative narratives to give a representation of the HCV transmission network in PWID. This network was then used in an individualbased model (IBM) testing different treatment strategies.

Results

Sixty-nine PWID participated in the HCV bio-behavioural and social network surveys. The estimated prevalence of HCV was 29% (95% CI 13.3-44%) and the estimated total population size was 262 individuals.
The social network survey described 179 PWID, connected together into a cohesive network component via injecting partnerships. Phylogenetic analysis indicated that a number of these partnerships had led to the transmission of HCV and that genotype 3a virus had been transmitted between PWID living on the IOW. 
In the IBM the preferential treatment of well-connected PWID, via injecting and social relationships, led to significantly fewer new infections of HCV than treating at random (9.56 vs. 6.58 P<0.01 and 9.56 vs. 7.84 p=0.011 respectively).

Conclusion

The burden of HCV in PWID on the IOW is lower than expected and existing case-finding initiatives are effective. The qualitative and quantitative results indicate that PWID are linked together in a dense network and the treatment of well-connected nodes within this network may be an effective treatment as prevention strategy for the elimination of HCV on the IOW.

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Identifiers

ORCID for Salim Khakoo: orcid.org/0000-0002-4057-9091

ORCID for Julie Parkes: orcid.org/0000-0002-6490-395X

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