Re-emerging syphilis: a detrended correspondence analysis of the behaviour of HIV positive and negative gay men.

C Philip Wheater,Qutub Syed,Pete Clark,Mark A Bellis,Penny A Cook

doi:10.1186/1471-2458-3-34

Abstract

BackgroundRecent syphilis outbreaks in the UK have raised serious concerns about the sexual health of the population. Moreover, syphilis appears more likely to facilitate HIV transmission than any other sexually transmitted infection (STI).MethodsThe sexual and other risk behaviour of a sample of HIV positive and negative gay men with and without syphilis was subjected to a detrended correspondence analysis (DCA).ResultsA DCA plot was used to illustrate similarity of individuals in terms of their behaviours, regardless of their infection status. The majority of those with syphilis (78%; 18/23) fell into a high-risk group with more partners, and use of anonymous sex venues and drugs during sex. However, 16% of uninfected controls (8/49) and 62% of HIV positive individuals without syphilis (8/13) also fell into this high-risk group.ConclusionsUsing a statistical technique that is novel for this type of investigation, we demonstrate behavioural overlaps between syphilis-infected individuals in an ongoing UK outbreak and uninfected HIV positive and negative controls. Given the high-risk behaviour of a significant proportion of uninfected individuals, ongoing transmission of syphilis and HIV in this population seems likely.

Highlights

Recent syphilis outbreaks in the UK have raised serious concerns about the sexual health of the population
Once detrended correspondence analysis (DCA) had been used to produce a two-dimensional plot of the major variation in the dataset, individuals were labelled with their infection status (Fig. 1)
Analysis showed that a higher degree of discrimination was achieved using both ordination axes compared to using the major axis of variation alone (71.8%)

Summary

Introduction

Recent syphilis outbreaks in the UK have raised serious concerns about the sexual health of the population. Syphilis appears more likely to facilitate HIV transmission than any other sexually transmitted infection (STI). Behaviour change among gay men in the early 1980s in response to the AIDS crisis contributed to a reduction in HIV transmission and that of other sexually transmitted infections (STIs) [1]. Recent increases in STIs and outbreaks of less common STIs such as syphilis amongst gay men in several UK locations [2,3] and elsewhere in Europe [4] raise concerns over complacency about safe sex among gay men. STIs such as syphilis may interact with HIV and exacerbate HIV transmission [5].

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Conclusion