A highly resistant strain of rapidly progressive HIV has been found in a New York man who had not previously undergone antiviral drug treatment.

According to the Department of Health and Mental Hygiene the new strain of virus, called 3-DCR HIV, does not respond to medication and appears to greatly shorten the interval between HIV infection and the onset of AIDS.

Health experts say the strain has not been detected anywhere else in the world and is "difficult or impossible to treat.”

The man was first diagnosed with HIV in December 2004 and appears to have been recently infected. The diagnosis of 3-DCR HIV was made shortly afterwards and since then the patient has developed AIDS.

Counselling and HIV testing is already being offered to partners of the man, who is said to have used crystal meth during sex with other men.

While drug resistance is increasingly common among patients who have been treated for HIV, cases of 3-DCR HIV in newly-diagnosed, previously untreated patients are extremely rare.

The discovery has prompted renewed warnings from city health officials for people to practise safe sex.

"This case is a wake-up call. First, it's a wake up call to men who have sex with men, particularly those who may use crystal methamphetamine,” said Health Commissioner Thomas R. Frieden.

“Not only are we seeing syphilis and a rare sexually transmitted disease - lymphogranuloma venereum - among these men, now we've identified this strain of HIV that is difficult or impossible to treat and which appears to progress rapidly to AIDS.

“This community successfully reduced its risk of HIV in the 1980s, and it must do so again to stop the devastation of HIV/AIDS and the spread of drug-resistant strains.”

However the New York Times reports that some Aids specialists outside New York have cast doubt on the alarm, saying that the man's immune system may already have been compromised.