Early and continuous antiretroviral therapy advocated by Swiss to stop HIV transmissions in gay men

Most new HIV infections amongst gay men in Switzerland originated in individuals with chronic HIV infection, investigators report in the online edition of AIDS.

Transmission clusters were mapped amongst gay men recently infected with HIV in Zurich and in the Swiss HIV Cohort. Only two infections appeared to originate from individuals with very recent HIV infection. In all other cases, the source patient was an individual who had been infected with HIV for at least one year.

“Infectiousness during chronic infection was quite high in this population”, comment the investigators.

None of the individuals transmitting HIV was taking antiretroviral therapy and had an undetectable viral load.

The investigators believe that their findings support “early” and “continuous” use of HIV treatment by gay men, and suggest that this could profoundly slow the HIV epidemic in this population.

There is a continuing HIV epidemic amongst gay men. An in-depth knowledge of the dynamics of HIV transmission could assist in the development of targeted prevention campaigns.

Therefore investigators from the Zurich Primary Infection study and the Swiss HIV Cohort study used phylogenetic analysis to map to transmission clusters in gay men recently infected with HIV.

The investigators were especially eager to see if individuals who had been infected with HIV very recently were the source of a large number of infections.

A total of 111 gay men recruited to the Zurich study before the end of 2007 were included in the investigators’ analysis, and were followed for a median of three years . A total of 93 of these individuals started antiretroviral therapy soon after their infection with HIV, with 51% discontinuing such treatment after one year.

Using phylogenetic analysis, the investigators identified six transmission clusters involving 20 men from the Zurich cohort and eight individuals from the wider Swiss cohort.

Only two infections appeared to originate in individuals with very recent HIV infection.

The rest had their source in chronically-infected individuals who had discontinued HIV therapy.

These individuals had plasma viral loads ranging from 314 to 1,690,000 copies/ml.

The investigator’s first analysis suggested that a patient taking HIV therapy with an undetectable viral load may have transmitted HIV to his partner. However, further genetic analysis found three other patients with more closely matched virus.

“We detected a remarkable proportion of new infections originating from index patients being already in their chronic phase”, comment the investigators. They add, “These findings argue strongly for early, continuous antiretroviral therapy in sexually active HIV-infected men who have sex with men. This strategy, most likely, will have a profound impact to reduce further spread of HIV.”