King County health officials announced on February 1 that four local gay men have been diagnosed with a similar, drug-resistant strain of HIV, and the health officials expressed concern that this “cluster” of hard-to-treat HIV cases could signal one particularly drug-resistant strain of HIV spreading in the local gay community.

“We’re calling these a ‘cluster’ because their resistance patterns are so similar that we think there may be a common source or sources,” said Dr. Bob Wood, the HIV/AIDS program director for the county’s health department. “We wanted to get the message out—particularly to people who might be having risky sex in the gay community—that HIV is bad, but some HIV is worse.”

The announcement was similar to an announcement made almost exactly two years ago by health officials in New York City, who had discovered a man infected with a strain of HIV that progressed quickly to full-blown AIDS and was resistant to three of the four classes of HIV drugs.

However, while in that case New York City health officials released information that gave a sense of the infected man’s age (mid-40s) and how he met his partners (over the internet), King County health officials refused to describe the age or sexual meeting places of the men in the local cluster, other than to say that they were all crystal-meth users who had anonymous sex with multiple partners, and that there was “variability” in their sexual meeting places.

“The behavior that got them infected was unsafe sex,” Dr. Wood said, explaining why the department wasn’t releasing more detailed information on their behaviors. “And probably the meth didn’t help.”

Dr. Wood said the men have not described having sex with each other, which suggests that if they do all have the same virus, there is at least one additional man in King County who gave it to them—or, perhaps, more than one man.

One of the men tested positive for HIV in 2005. The other three tested positive in 2006. The similarity of the men’s viruses was identified last month through genetic screening that is part of a growing local effort to track drug-resistant HIV. Dr. Wood said there is no indication that this strain of the HIV virus, if it is indeed one single strain, progresses faster than other strains or is more infectious. However, the four men all have a strain of the virus that is resistant to two classes of HIV drugs and is partially resistant to a third class.

There are about 400 new HIV diagnoses every year in King County, a number that has remained stable over the last decade, despite efforts by local gay-health organizations and public health officials to bring it down. About 100 people die from AIDS or HIV-related illnesses each year in King County.

Nationwide, drug-resistant strains of HIV are thought to make up only about 3 percent of new infections annually, and in King County the health department has identified only 12 other cases of drug-resistant HIV in the last six years. Thus, to have four similar cases appear within the span of about a year is unusual and suggests that one drug-resistant virus could be spreading more quickly in the local community than other drug-resistant strains have spread in the past.

Wood defended his department’s refusal to give out information about the men’s ages or sexual meeting places, saying his department couldn’t compromise their privacy. However, he did say that the men’s meth use “puts them in a smaller class of the gay community.”