ZONE:

A third of gay men with the HIV virus do not know they are infected and a growing number are engaging in unsafe sex with other men, a study by researchers from the Royal Free and University College Medical School, and Central Public Health Laboratory, has found.

The researchers who questioned more than 8,000 gay men in London's bars, clubs and saunas between 1996 and 2000 say that the numbers represent a serious public health concern.

"The high level of risky behaviour in HIV-positive men, regardless of whether they are diagnosed, is of public health concern in an era when HIV prevalence, anti-retroviral resistance and STI [sexually transmitted infections] incidence are increasing," the researchers said.

"High levels of unprotected anal intercourse continue to be reported by both HIV saliva antibody-positive and negative men, and the potential for onward transmission of HIV and increasing prevalence is a major public health concern."

Published in the journal Sexually Transmitted Infections, researchers say the study confirms fears that as many as one in three of the UK's estimated 50,000 HIV sufferers are unaware of their infection.

In 2000, they gathered anonymous saliva samples from 1,206 men to test their HIV status. About one in nine of the samples (10.9%) was positive for HIV. In a third of these cases - 43 out of the 132 - the HIV had not been diagnosed, and of those, the 4% who said they knew their HIV status - got it wrong.

In 1996, around one in three men (30%) said they had had unprotected sex in the last 12 months. By 2000, this figure had risen to more than four in 10 (42%). The team said that of the men having unprotected sex, 45% said they only did so with partners with the same HIV status.

The researchers also raised concerns that 16% of men who reported having a sexual relationship with same HIV status partners were either incorrect about their diagnosis or could not be completely sure about it as they had either never had an HIV test, reported their status incorrectly or did not know their HIV status.

The study concluded that as gay men continue to report increasing levels of unprotected anal intercourse, HIV prevalence remains high in this group, with many infections remaining undiagnosed.

Overall the study found that 10.9 per cent of the socially active gay men in London who took part in the survey were HIV-positive, as determined from tests for the presence of viral antibodies in saliva samples.