NEW YORK - For the first time, doctors have diagnosed a form of HIV that New York City health officials say has two striking characteristics: It is highly resistant to antiviral drugs in a patient who had never been treated with the medications, and it quickly develops into full-blown AIDS.

The infection defied the typical HIV-to-AIDS profile by apparently developing into AIDS in a matter of months, officials said.

''We've identified this strain of HIV that is difficult or impossible to treat and which appears to progress rapidly to AIDS,'' said New York City Health Commissioner Thomas Frieden. ``We have not seen a case like this before. It holds the potential for a very serious public health problem.''

''It is likely there are others infected with this strain and this individual has infected others,'' Frieden said.

The case is ''extremely concerning and a wake-up call,'' he said.

Dr. David Ho, director of Manhattan's Diamond AIDS Research Center, where the patient was diagnosed with HIV in December, said the combination of drug-resistant infection and ``his rapid clinical and immunological deterioration is alarming.''

The city Department of Health and Mental Hygiene has alerted health care professionals and has asked them to test all newly diagnosed HIV cases not previously treated with anti-viral medicines for possible drug resistance.

Resistant HIV strains have been seen before, but only in patients who have taken antiviral drugs over a period of years. And HIV infection generally takes 10 years or longer to transform into AIDS.

The patient in this case, a man in his mid-40s, was diagnosed with HIV in December and got the AIDS diagnosis recently.

He had been tested for HIV over the years and had never tested positive, or been treated, for the disease.

Officials said the man might have been infected earlier than his December diagnosis.

But even if the infection occurred 20 months earlier, they said, the speed of the transformation to AIDS would be striking.

The strain, termed 3-DCR HIV, resists three of the four antiviral drug classes. The patient has shown resistance to a total of 19 drugs.

Officials did not disclose his identity.

They said he had told them he had unprotected anal sex with multiple male partners in October.

They also said he had used crystal methamphetamine, a recreational drug that dulls inhibitions, leading to unsafe sexual practices.

''It is the only diagnosed and reported case in the country that we are aware of in which the patient has received no previous drug treatment for HIV but has resisted the drugs and rapidly progressed to AIDS,'' city Health Department spokesman Sid Dinsay said.

City officials are consulting with the Centers for Disease Control and Prevention in Atlanta.

In a telephone interview, Dr. Ronald Valdiserri, deputy director of CDC's National Center for HIV, STD and TB Prevention, termed the case ''very concerning,'' citing ''the intersection of the two phenomena that were reported'' -- the drug resistance and swift progression to AIDS.

He urged people being treated for HIV or AIDS not to risk becoming infected with the new strain.

Officials said efforts are under way to contact the man's sexual partners to offer them counseling and HIV testing.