Gay men believe an undetectable viral load makes people with HIV less infectious

Both HIV-positive and HIV-negative gay men who believe that an undetectable viral load makes people with HIV less infectious are more likely to have unprotected anal sex, according to an American study presented to the XIV International AIDS Conference in Barcelona today.

Investigators from the AIDS Research Institute at the University of San Francisco recruited 533 gay men in San Francisco through community organisations and street outreach programmes and asked them to complete a questionnaire about their HIV status, viral load, and sexual behaviour over the past three months.

Thirty six percent of the sample was HIV-positive, with a little over two thirds receiving HAART. The average viral load amongst the positive sample was 18,000 copies/ml, with 58% of those receiving HAART reporting an undetectable viral load.

High risk sexual behaviour, defined as insertive unprotected anal sex with an HIV-negative man or partner of unknown HIV status, was reported by 13% of HIV-positive men in the study. Amongst HIV-negative men, unprotected receptive anal sex was defined by the investigators as the highest risk behaviour and was reported by 11% of the sample.

Over half (53%) of the HIV-negative gay men and 43% of the HIV-positives believed that the likelihood of transmitting HIV was reduced if a man with HIV had an undetectable viral load. Both positive and negative men who believed that an undetectable viral load made a person with HIV less infectious were more likely to engage in high risk sexual behaviour. Amongst the HIV-positive men, predictors of high risk behaviour included the belief that an undetectable viral load made them less infectious; their last viral load test showing an undetectable viral load; and taking HAART.

Viral load was discussed when sexual behaviour was being negotiated and where one partner was positive and the other negative, with 21% of HIV-negative men requesting information about their partner's viral load before deciding whether to have unprotected receptive anal sex.

The study did not report if any of the HIV-negative sample who believed that an undetectable viral load made positive men less infectious, contracted HIV.

The San Francisco study concludes that doctors should discuss viral load and beliefs about infectiousness with their patients, with discussion focusing on differences between viral load levels in genital fluids and the blood.