In 2004, a New York City man was infected with HIV and went on to develop AIDS in a remarkably short time period -- less than 20 months from the time of infection, whereas progression from infection with HIV to AIDS generally occurs over a period of eight to ten years. Also alarming was the fact that the man's HIV strain was resistant to most antiretroviral drugs, despite the fact that he had never taken antiretrovirals. Was this a new strain of HIV, a "superbug" that couldn't be stopped with drugs and caused AIDS in months, not years? With only a single affected patient, it was impossible to say.

Thus began a public health investigation by the New York City Department of Health and Mental Hygiene. A report describing the investigation and its findings was published last week in the Center for Disease Control and Prevention's Morbidity and Mortality Weekly Report: read the account of the scientific detective work here. Bottom line: three patients infected with a similar strain of HIV were identified; as of last month, at least two of these patients, along with the original patient, were clinically stable and responding to antiretroviral treatment.

But many questions remain: the investigation was unable to determine exactly when or how the original patient and the three other patients were infected, whether the multi-drug resistant HIV strain from each patient was the result of a single point of infection or from recombination or superinfection, and the actual prevalence of this HIV strain in NYC and elsewhere. Investigators are also unable to say if this particular strain is actually associated with rapid progression to AIDS or if other factors were responsible for the unusual course of the original patient's disease. One conclusion that can be drawn is that transmission of multi-drug resistant HIV is a significant public health problem and points to a resurgence in unsafe sex, particularly among men who have sex with men.