San Francisco has the highest percentage of gay men in the world and a quarter of them are HIV positive

Benjamin Cohen:

"Despite an overall loss in the population in San Francisco in the last five years, we think there has been an absolute gain in gay men," William McFarland, head of HIV/AIDS statistics at San Francisco's Department of Public Health, said in an interview. "From all the data I have seen ... it's the gayest city in the world."

The report estimates that there are roughly 63,577 gay males aged 15 and above living the the city which has a total population of 764,000. Of those residents who are male adults, one in five are gay.

One quarter, 25.8 per cent of the gay male population is infected with the HIV virus resulting in the city being home to 16,401 HIV positive men.

"The major changes since 2001 are that, first of all, the gay community has grown. It's largely been an influx of more HIV-negative gay men that are here," Mr Mc Farland said. "It used to be near 30 percent.

"The absolute number of gay men living with HIV has crept up partly because of ongoing transmission and partly because of improved survival with treatment," he added.

Baltimore is believed to have the highest percentage of HIV positive gay men in its population with some 40 per cent infected according to a 2005 Disease Control and Prevention study.

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