New York- A unique strain of HIV resistant to most major kinds of antiviral therapy has been diagnosed in a patient in New York City, raising concern among public-health experts about the potential of the AIDS virus to overcome treatments that can keep the disease in check.

The strain also caused an unusually rapid onset of full-fledged AIDS in the patient. New York Health Department officials said he may have developed the disease only two or three months after his initial infection–far shorter than the normal lag of nine to 11 years between HIV infection and AIDS.

Health experts stressed that they know of only a single case involving the strain, and the rapid progression to AIDS may have more to do with the patient’s susceptibility than with the strength of the virus. Still, worries about the case prompted the New York Health Department and the federal Centers for Disease Control and Prevention to send warnings to health departments around the country.

“It’s very alarming,” said Dr. Ron Valdiserri, deputy director of the CDC’s National Center for HIV, STD and TB Prevention. “We would hope that this case could serve as a wake-up call that we’re still dealing with a very formidable adversary in HIV.”

New York health officials described the patient as a man in his mid-40s who had unprotected anal intercourse with multiple male partners, often while using crystal methamphetamine. HIV was diagnosed in December 2004. Officials said they are tracing the patient’s sexual contacts to notify them and gauge any spread of the strain.

Rates of drug resistance slowly have increased since a wave of new pharmaceuticals revolutionized HIV treatment nearly a decade ago. About half of HIV patients develop some resistance to at least one of the drugs they take for the infection–a problem that doctors often can deal with in the short term by prescribing different drugs.

The New York case is different because the man’s virus was resistant to three of the four commonly used classes of HIV therapies even though he never had received anti-HIV drugs. That suggests the highly resistant strain was passed directly from another infected person–raising the possibility that such dangerous strains could gain a foothold in the general population.