More frequent testing cuts HIV infections among MSM

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More frequent testing followed by treatment with available antiretroviral drugs may cut human immunodeficiency virus (HIV) infections by 66% among men having sex with men (MSM), according to a study of 617 Dutch men. Researchers say that this strategy could help turn the tide on the HIV epidemic among MSM, which has remained largely unconstrained in most countries, despite the scale-up of comprehensive care and prevention services in the past 20 years.

Antiretrovirals offer a highly effective treatment strategy for HIV infection, including as preventative treatment, called pre-exposure prophylaxis (PrEP), for uninfected, high-risk individuals. However, the number of new infections among MSM has remained constant in countries such as the Netherlands, the UK, Australia, Switzerland, and British Columbia, suggesting potential limitations with current prevention strategies.

To find out why, Oliver Ratmann and colleagues at the Imperial College London tracked the sources of HIV transmission among 617 recently infected MSM in the Netherlands across all stages of infection and care. Using viral genetic sequence and clinical patient data, they traced 71% of transmissions to undiagnosed men and the remaining 29% to men who were diagnosed but not yet treated, who initiated antiretroviral therapy, or who received no care for 18 months or more.

About 43% of the 617 men were infected by men in their first year of infection. Analysis revealed that if half of all men at risk of transmission had tested annually, immediate antiretroviral therapy to those testing positive and PrEP to half of all men testing negative could have prevented about 66% of HIV infections.

This test-and-PrEP-and-treat strategy could help guide the design of HIV prevention services to MSM in the Netherlands and similar countries, the researchers say.

New HIV diagnoses among men having sex with men (MSM) have not decreased appreciably in most countries, even though care and prevention services have been scaled up substantially in the past 20 years. To maximize the impact of prevention strategies, it is crucial to quantify the sources of transmission at the population level. We used viral sequence and clinical patient data from one of Europe’s nationwide cohort studies to estimate probable sources of transmission for 617 recently infected MSM. Seventy-one percent of transmissions were from undiagnosed men, 6% from men who had initiated antiretroviral therapy (ART), 1% from men with no contact to care for at least 18 months, and 43% from those in their first year of infection. The lack of substantial reductions in incidence among Dutch MSM is not a result of ineffective ART provision or inadequate retention in care. In counterfactual modeling scenarios, 19% of these past cases could have been averted with current annual testing coverage and immediate ART to those testing positive. Sixty-six percent of these cases could have been averted with available antiretrovirals (immediate ART provided to all MSM testing positive, and preexposure antiretroviral prophylaxis taken by half of all who test negative for HIV), but only if half of all men at risk of transmission had tested annually. With increasing sequence coverage, molecular epidemiological analyses can be a key tool to direct HIV prevention strategies to the predominant sources of infection, and help send HIV epidemics among MSM into a decisive decline.

Science Mag material
Science Translational Medicine abstract

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