BACKGROUND:
In
the UK HIV epidemic, historically dominated by subtype B transmission among men
who have sex with men (MSM), 50% of diagnoses and prevalent infections are now
heterosexual, mainly non-B subtypes. Between 2002 and 2010 non-B diagnoses
among MSM increased from 5.4% to 17% and this study has focused on the drivers
of this change.
METHODS:
Growth
between 2007 and 2009 in transmission clusters among 14,000 subtype A1, C, D
and G sequences from the UK HIV Drug Resistance Database was analysed by risk
group.
RESULTS:
Of 1148
clusters containing at least two sequences in 2007, >75% were pairs and
>90% were heterosexual. Most clusters (71.4%) did not grow during the study
period. Growth was significantly lower for small clusters, and higher for
clusters ≥7, being highest for clusters comprising sequences from MSM and
people who inject drugs (PWID). Risk group (p<0.0001), cluster size
(p<0.0001) and subtype (p<0.01) were predictive of growth in a
generalized linear model.
DISCUSSION:
Despite
the increase in non-B subtypes associated with heterosexual transmission, MSM
and PWID are at risk for non-B infections. Crossover of subtype C from
heterosexuals to MSM has led to the expansion of this subtype within the UK.
Below: Figure 1: Risk group classification of clusters (2009). 2327 clusters (304
A1, 1785 C, 113
D, 125 G)
contained at least two sequences: 1630 clusters were pairs and 681 comprised
more than two sequences.
MSM men who have sex with men, HET heterosexual, PWID
people
who inject drugs, NA not available
- 1Institute for Evolutionary Biology, University of Edinburgh, Edinburgh, UK.
- 2The Roslin Institute, University of Edinburgh, Edinburgh, UK.
- 3London School of Hygiene and Tropical Medicine, London, UK.
- 4MRC Clinical Trials Unit at UCL, London, UK.
- 5Public Health England, London, UK.
- 6Institute for Evolutionary Biology, University of Edinburgh, Edinburgh, UK A.Leigh-Brown@ed.ac.uk.
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