Blood rather than semen mode of HCV transmission in HIV-positive gay men

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Contact with blood rather than semen explains the sexual transmission of hepatitis C virus in HIV-positive gay men, German investigators suggested at the 12th European AIDS Conference in Cologne.

Fisting, group sex, and snorting drugs emerged as significant risk factors for sexual transmission of hepatitis C. Unprotected anal sex in the absence of these risk factors was not associated with transmission of the virus, and the investigators believe that their findings should lead to the refocusing of hepatitis C prevention campaigns for HIV-infected gay men which have largely stressed the risk factors of unprotected sex.

Since 2000 outbreaks of sexually transmitted hepatitis C have been reported amongst HIV-positive gay men in a number of large northern European cities including London, Amsterdam and Berlin. Unprotected anal sex and fisting were quickly identified as risk factors.

Glossary

rectum

The last part of the large intestine just above the anus.

receptive

Receptive anal intercourse refers to the act of being penetrated during anal intercourse. The receptive partner is the ‘bottom’.

multivariate analysis

An extension of multivariable analysis that is used to model two or more outcomes at the same time.

epidemiology

The study of the causes of a disease, its distribution within a population, and measures for control and prevention. Epidemiology focuses on groups rather than individuals.

confounding

Confounding exists if the true association between one factor (Factor A) and an outcome is obscured because there is a second factor (Factor B) which is associated with both Factor A and the outcome. Confounding is often a problem in observational studies when the characteristics of people in one group differ from the characteristics of people in another group. When confounding factors are known they can be measured and controlled for (see ‘multivariable analysis’), but some confounding factors are likely to be unknown or unmeasured. This can lead to biased results. Confounding is not usually a problem in randomised controlled trials. 

A higher hepatitis C viral load has been observed in the semen of HIV-infected men and this could explain the increased risk of sexual transmission of the virus seen in this population. However, there is little evidence of sexual acquisition of hepatitis C in the HIV-negative partners of HIV-positive gay men. Nor is there evidence of sexual transmission of the virus in HIV-positive heterosexual couples where one partner is also infected with hepatitis C.

To gain a better understanding of the risk factors for sexual transmission of hepatitis C, investigators in Bonn conducted a case-controlled study involving 34 gay men co-infected with HIV and hepatitis C and 67 age-matched men who were only infected with HIV. None of the men reported injecting drug use.

The men were recruited to the study between 2006 and 2008. They provided information on their sexual and drug use behaviour, and also stated if they had experienced rectal bleeding as a consequence of sex.

Unprotected anal sex was widely reported, and approximately 50% of men reported receptive fisting.

The first set of statistical analysis showed that several risk factors were associated with infection with hepatitis C including use of sex toys, rectal bleeding, receptive fisting without gloves, and the snorting of stimulant drugs such as cocaine and amphetamines during group sex.

Multivariate analysis that controlled for potential confounding factors showed that only receptive fisting (p = 0.007), rectal bleeding (p = 0.007) and drug use during group sex (p = 0.02) were significantly associated with sexual transmission of hepatitis C.

The investigators therefore suggested that the virus was being transmitted via blood rather than semen, and that uninfected insertive partners were acting as vectors of transmission during group sex sessions.

However, not all delegates to the conference were convinced by these findings. A questioner from the floor pointed out that many HIV-positive patients with acute hepatitis C infection in London did not report fisting.

Moreover, Dr Sanjay Bhagani told aidsmap.com that it was his sense that the epidemiology of hepatitis C amongst HIV-positive gay men in London was changing and that many infections could probably be attributed to injecting drug use rather than sex.

Nevertheless, the investigators conclude that prevention messages should inform at HIV-positive gay men of the risks of hepatitis C that arise from long-lasting, group-sex sessions where there is rectal trauma caused by activities such as fisting.

References

Schmidt AJ et al. The trouble with bleeding: why do HIV-positive gay men get hepatitis C?. 12th European AIDS Conference, Cologne, BPD 1/7, 2009.

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