Increased rates of unprotected sex among undiagnosed gay men wipe out benefits of diagnosis and HIV treatment

Michael Carter
Published: 14 August 2012

The ongoing HIV epidemic among gay men in the Netherlands is due to increased rates of unprotected sex, investigators report in the online edition of AIDS.

Higher rates of risky sex, especially among undiagnosed individuals and men who are not taking anti-HIV drugs, are offsetting the benefits provided by testing and antiretroviral treatment.

“The resurgent epidemic in the Netherlands as a whole can be satisfactorily…explained by increased risk behaviour, predominantly in undiagnosed individuals,” write the authors.

Gay men continue to be a main focus of the HIV epidemic. Diagnoses have increased in recent years, and there is some evidence that HIV incidence in gay men is also on the rise.

Possible causes of the ongoing and possibly resurgent HIV epidemic in gay men include high rates of unprotected sex involving individuals who are unaware of their infection and those who are not taking treatment and the high rates of other sexually transmitted infections that are present in gay men.

An international team of investigators wanted to get a clearer understanding of the causes.

They therefore developed a mathematical model that was based on annual data for HIV and AIDS diagnoses in the Netherlands between 1980 and 2009. Incorporated into the model were assumptions about the efficacy of HIV therapy, and the infectiousness of individuals during the acute and chronic phases of HIV infection, as well as the impact of suppressive antiretroviral therapy on the risk of transmission.

Using this model, the investigators calculated transmission and diagnoses rates.

These were also estimated using information obtained from the Amsterdam Cohort Study. This was established in 1984 and the investigators focused on data concerning the proportion of HIV-negative men reporting unprotected anal sex in the previous six months with another man.

There was agreement between the two models. Both showed that risk behaviour fell by approximately a half between the mid-1980s and the mid-1990s. This limited the spread of HIV among gay men.

However, incidence then increased. This was primarily driven by increased rates of unprotected anal sex involving undiagnosed men.

“The increase in risk behaviour among untreated individuals is offsetting benefits in terms of reduced incidence offered by enhanced testing and treatment, which reduce transmission,” comment the investigators.

Thanks to the health benefits of antiretroviral therapy, there was no evidence that the resurgent epidemic was associated with increased mortality rates. “However the long-term healthcare costs and infection-associated morbidity will likely be substantial,” warn the authors.

They conclude, “reductions in incidence could be obtained by increasing rates of diagnoses, by reducing time to initiate antiretroviral therapy, and by encouraging individuals to practice safe sex.”


van Sighem A et al. Increasing sexual risk behaviour amongst Dutch MSM: mathematical model versus prospective cohort data. AIDS 26, online edition. DOI: 10/1097/QAD.0b013e3283574df9, 2012.

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