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Non-disclosed men who have sex with men in UK HIV transmission networks: phylogenetic analysis of surveillance data

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Original languageEnglish
Pages (from-to)e309–e316
JournalLancet HIV
Volume5
Issue number6
DOIs
Publication statusPublished - 1 Jun 2018

Abstract

BackgroundPatients who do not disclose their sexuality, for example men who do not disclose same-sex behaviour, are extremely difficult to characterise through traditional epidemiological approaches. Using a recently developed method to detect large networks of viral sequences from time-resolved trees, we have localised these men in UK transmission networks, gaining critical insights into the behaviour of this group. 
Methods We obtained HIV pol sequences from the UK HIV Drug Resistance Database (UKRDB), a central repository for resistance tests performed as part of routine clinical care throughout the UK. Sequence data are linked to demographic and clinical data held by the UK Collaborative HIV Cohort study and the national HIV/AIDS Reporting System database. Initially we reconstructed maximum likelihood phylogenies from sequences from over 50,000 individuals in the UK. Sequences were selected for time-resolved analysis in BEAST if they were clustered with at least one other sequence at a genetic distance ≤4.5% with support ≥ 90%. We used time-resolved phylogenies to create networks by linking together nodes if sequences shared a common ancestor within the previous 5 years. We identified potential nondisclosed MSM (pnMSM) as self-reported heterosexual men who clustered only with men. We measured the network position of pnMSM, including betweenness (a measure of connectedness and importance) and assortativity ((the propensity for nodes sharing attributes to link).
Findings14,405 individuals were represented in the network, including 8,452 MSM, 1743 heterosexual women and 1341 male heterosexuals. 249 pnMSM were identified (18.6% of all clustered heterosexual men). pnMSM were more likely to be Black-African (p<0.0001) and were slightly older (39.00 vs. 36.38 p=0.002) than the MSM they clustered with. Betweenness centrality was lower for pnMSM than for MSM (1.31 vs 2.24, p=0.002), indicating that they were in peripheral positions in MSM clusters. Assortativity by risk group was higher than expected (0.037 vs - 0.037, p=0.01) signifying that pnMSM linked to each other. We found that self-reported male heterosexuals were more likely than heterosexual women to link MSM and heterosexuals (Fisher’s exact test; p=0.0004; OR 2.24) but the number of such transmission chains was small (only 54 in total compared to 32 in women).
InterpretationWe have shown that pnMSM are a subgroup distinct from both MSM and from male heterosexuals. Male heterosexuals are the group most likely to be diagnosed in late stage disease, and nondisclosed MSM may put female partners at higher risk. Thus, pnMSM require specific consideration to ensure they are included in public health interventions.

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