The use of antiretroviral treatment appears
to have stabilised the HIV epidemic in Danish gay men, even though rates of
risky sex have increased, research published in the online edition of the Journal of Acquired Immune Deficiency
“While unsafe sex among MSM [men who have
sex with men] has increased substantially and the number of HIV-positive MSM
living in Denmark has enlarged, the incidence of HIV diagnoses in this
population has remained stable for more than a decade,” write the authors. “Our
findings indicate that this paradox is due to effective antiretroviral therapy
and not increased awareness of safe sex.”
The investigators believe that the HIV
epidemic in Danish gay men is being sustained by undiagnosed people and diagnosed people who are not yet on antiretroviral therapy.
There is growing interest in the use of HIV
treatment as prevention. Studies conducted in heterosexual people show that the risk
of sexual transmission of the virus is negligible if a patient is on HIV treatment and has an undetectable viral load.
Data showing the impact of antiretroviral
therapy on the HIV epidemic in gay and other MSM are largely lacking.
However, investigators in Denmark
hypothesised that antiretroviral therapy was indeed preventing new infections
in gay men.
They examined three data sources to see if
this was indeed the case. These sources provided information on: HIV prevalence
and the number of new diagnoses; the sexual risk behaviour of gay men; and the
incidence of syphilis.
Between 1995 and 2009, there was a median
of 93 new HIV diagnoses in gay men per year. There was evidence of a modest
decline in new diagnoses in the late 1990s, followed by a vague increase until
2005, when the number of new diagnoses stabilised.
Other surveillance data showed that the
number of undiagnosed infections in the country remained largely unchanged at
approximately 500 people.
During the period of the study, there was a
75% increase in the number of HIV-positive gay men who were alive and living in
Denmark from 1035 in 1995 to 1813 in 2010.
Over the same period, the number of
HIV-positive gay men with a viral load above 400 copies/ml fell from 1035 to
The investigators calculated that HIV
incidence in gay men (Cohort Community Reproductive Rate, or CCRR) was 0.099 in
1995. This fell steadily through the late 1990s and stabilised at 0.071 from
This fall in HIV incidence was accompanied
by an increase in the proportion of HIV-positive men with virologic suppression.
It was apparent that this stabilising of
the epidemic was due to antiretroviral therapy rather than changes in sexual
Data from the annual Sex Lives Survey
showed there were year-on-year increases in unsafe sex. Respondents reported an
increasing number of partners with whom they had anal sex (p < 0.01),
increased frequency of unprotected anal intercourse (p < 0.01) and an
increase in the number of partners of unknown HIV status (p < 0.01).
Men with diagnosed HIV infection were
significantly more likely to report risky sexual behaviour than HIV-negative
Syphilis surveillance data also suggested
that gay men were having more risky sex. The annual number of diagnoses
increased from just 2 in 1995 to 208 in 2009.
“The present study suggests that successful
implementation of HAART [highly active antiretroviral therapy] has had a major
impact on HIV incidence among MSM,” comment the investigators.
The investigators believe there are two
sources of new infections: diagnosed patients who are not yet taking
antiretroviral treatment and a constant pool of approximately 500 undiagnosed
“Earlier models have suggested that there
may be a balancing point at which increasing levels of high risk sexual
behaviour performed by a large number of undiagnosed/untreated HIV-positive MSM
offsets the effect of early/regular HIV-testing…and subsequent treatment of
those diagnosed as HIV-positive,” note the researchers. “This point seems to
have been reached among MSM in Denmark in the early 2000s.”
They therefore conclude “additional
measures to diminish the pool of MSM who are at risk of transmitting HIV should
focus both on earlier initiation of HAART and enhanced testing, especially of
MSM engaged in sexual risk behaviour”.