The CDC reports a big increase in the number of men having unprotected anal sex — from 48% of gay and bisexual males in 2005 to 57% in 2012

About a third of the men surveyed hadn't been tested for HIV within the past year. It's not that concerns about contracting HIV have vanished, it's that more gay men are using a strategy known as "sero-sorting," says CDC chief Thomas Frieden. The strategy — playing off the phrase "HIV seronegative" on lab reports — refers to an uninfected man who has sex only with other uninfected men, or at least men who think they are. “The problem with sero-sorting is that it’s really easy to get it wrong," says Frieden. The number of new HIV infections in the United States per year has held steady at about 50,000 in recent years, the study's lead researcher said. But considering that 65% of new infections are the result of men having sex with other men, "we are concerned about the increase," she says.