A new study in the United Kingdom shows that one third of HIV-positive gay men are unaware that they're infected with the virus, Glasgow's The Herald reports. Researchers tested more than 1,200 gay men at London bars, clubs, and saunas for HIV antibodies, and 10.9% of the tests came back positive for HIV infection. Two-thirds of the men already knew they were HIV-positive, but one-third of the men who tested positive were previously unaware they were infected. Of the men who said they knew their HIV status before being tested, 4% were wrong about it. The researchers say the reason for the high percentage of gay men unaware they are infected with HIV is because of a lack of regular HIV testing and an increase in unsafe sex that is spreading the virus. Their studies show that about 42% of the men surveyed had reported having unprotected sex during the previous year, an increase of more than 12% when the same question was asked in a 1996 survey. "High levels of unprotected anal intercourse continue to be reported by both [HIV-positive] and negative men and the potential for onward transmission of HIV and increasing prevalence is a major public health concern," the researchers conclude. Their full study appears in the journal Sexually Transmitted Diseases.