HIV incidence (the new infection rate) is falling among injection drug users (IDUs) and heterosexuals in Scotland, but incidence is not falling among men who have sex with men (MSM).

Researchers analyzed data from the national HIV test database for everyone tested at least once in Scotland from 1980 to 2009. They calculated incidence for MSM, IDUs, and heterosexuals for the entire period and compared rates before 1995 and in 2005-2009.

Of the 59,807 people tested for HIV, 620 had a positive test after an initial negative test. Overall incidence was 3.7 per 1000 person-years (95% confidence interval [CI] 3.4 to 4.0). Most of the 620 new infections (60%) were among MSM, while heterosexuals accounted for 37% of new infections and IDUs for 20%.

Overall incidence among MSM (15.3 per 1000 person-years, 95% CI 13.8 to 17.0) remained relatively stable when the researchers compared the years before 1995 and 2005-2009.

In contrast, incidence among IDUs fell from 5.1 to 1.7 per 1000 person-years before 1995 to 1.7 per 1000 person-years in 2005-2009. Incidence for those two periods also fell for heterosexuals, from 2.9 to 1.4 per 1000 person-years.

The authors believe “the reduction in the incidence rate among IDUs suggests that harm reduction measures initiated from the late 1980s were effective in reducing HIV transmission in this risk group.”

But they stress that “the absence of a reduction in HIV incidence rates among MSM is disappointing and highlights the need for renewed efforts in the prevention of HIV in this major risk group.”

Source: Scott A. McDonald, Sharon J. Hutchinson, Lesley A. Wallace, Sheila O. Cameron, Kate Templeton, Paul McIntyre, Pamela Molyneaux, Amanda Weir, Glenn Codere, David J. Goldberg. Trends in the incidence of HIV in Scotland, 1988-2009. Sexually Transmitted Infections. 2012; 88: 194-199.

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By Mark Mascolini