Hoping to unravel a mystery that baffled scientists at a world AIDS conference last week, federal health officials plan to ask the nation's doctors to report any cases of patients who have acquired immune deficiency syndrome but lack the virus usually linked to the disease.
Dr. Anthony Fauci, director of AIDS research for the National Institutes of Health, said yesterday that the federal Centers for Disease Control and the NIH would put out the call in an attempt to learn whether the phenomenon was widespread and if a new virus was at work.
"We will make a call to the clinical and research community involved in seeing AIDS patients, asking that if they see any patients who fall into this category, to let us know," Dr. Fauci said yesterday.
The CDC will investigate any new cases to see if they were transmitted from person to person and, if so, by what means. Meanwhile, the NIH will arrange for sophisticated tests to determine if a new virus or some other agent is responsible.
The NIH will conduct the tests at its own labs, make its facilities available to doctors reporting the cases or refer physicians to outside laboratories capable of doing the scientific detective work.
"We're going to look at what we have and search for what we don't have," Dr. Fauci said.
At the eighth International Conference on AIDS, a handful of doctors reported about 30 cases of patients who had the deadly disease but tested negative for the human immunodeficiency virus, or HIV.
The cases were reported by doctors from Los Angeles, New York, Edinburgh in Scotland and The Hague in the Netherlands. The cases apparently did not appear in clusters that could indicate transmission inside circles of sexual partners, drug contacts or blood recipients, although it is possible that unrecognized cases are being transmitted that way.
Many scientists have cast doubt on a California doctor's report that he isolated a new virus in a 66-year-old woman with AIDS-like symptoms and in her healthy daughter. Dr. Fauci and others have suggested that the scientist might have been fooled by a stray virus that contaminated blood samples taken from the two women.
In the wake of the conference, the federal agencies appeared to be moving swiftly to unravel the mystery after drawing criticism that they failed to apprise the scientific community earlier about evidence of six cases it has accumulated over the past two years.
Many scientists said the CDC should have published the findings in their widely read weekly report and should have put out a call for doctors to report any similar cases.
Until last week, most authorities assumed that two related viruses, HIV-1 and HIV-2, were the agents responsible for almost 260,000 cases of AIDS in the United States and about 2 million worldwide.
Without more data, Dr. Fauci said, it is impossible to know whether there have been just a few cases of AIDS without HIV since the epidemic surfaced a decade ago, or if it is a more widespread phenomenon that had gone undetected. Officials with the World Health Organization said last week they would hold a global meeting soon to determine the extent of the cases worldwide.
Dr. Fauci said he thought scientists were now looking at a "new phenomenon" -- AIDS without HIV infection -- but he saw no evidence yet of a public health threat. One reason is the absence of clusters that characterized the spread of AIDS early in the epidemic.
At the same time, Dr. Fauci said he doubted the phenomenon was simply a matter of the familiar HIV hiding out in tissues and evading detection, as some experts have suggested.
"My gut reaction is that we're probably dealing with a newly recognized phenomenon or an increase in a phenomenon that was background noise in the past," he said.