The Eighth International AIDS Conference in Amsterdam last month ignited a heated controversy over reports of at least 30 patients in the U.S. who appear to have AIDS but do not test positive for HIV. Since then, three teams of scientists have weighed in with evidence suggesting culprits. Researchers at Cornell Medical Center in New York, led by Dr. Jeffrey Laurence, studied the blood cells of five non-HIV AIDS patients. The team found evidence of a previously unknown retrovirus in the same family as HIV in blood samples from these patients, according to Stephen S. Morse, a virologist at Rockefeller University and co-author of a paper Laurence submitted to the Lancet, a British journal. "We're quite sure it's not HIV-1 and reasonably sure it's not HIV-2," says Morse.

A second group, at the Aaron Diamond AIDS Research Center, also in New York, takes issue with Laurence's work, says staff investigator John P. Moor. The Diamond researchers, headed by David Ho, say they have found a different retrovirus in their samples that is not related to HIV. Moor cautions that the team has yet to establish a connection between this new virus and AIDS. In fact, he says, when a person's immune system is suppressed, the body it can harbor all sorts of foreign invaders. Says Moor: "The question is, is the virus a cause or contaminant?"

At the University of California at Irvine, meanwhile, researcher Sudhir Gupta has isolated a completely different retrovirus from a 66-year-old woman with AIDS-like symptoms and from her unaffected 38-year-old daughter. Critics of Gupta's work say that, while he is a careful researcher, the type of virus he claims to have found--which he calls human intracisternal retrovirus--may be the same virus found in cultures taken from patients with other immune-system diseases, or it could also be a contaminant.

For now, most AIDS experts urge caution in interpreting all these results. "On the basis of what we know now, we can't say we are dealing with a new virus," says Dr. Anthony S. Fauci, head of the National Institutes of Health's AIDS efforts. "There have been many false starts before." Unexplained immunodeficiencies are nothing new--some are even inherited, notes William A. Haseltine, chief of the human retrovirology division at Harvard University's Dana-Farber Cancer Institute. His hunch is that researchers haven't looked hard enough for HIV-1 or other known retroviruses. Still, the questions about the risk to public health remain. "As for myself and the NIH," says Fauci, "we are assuming we are dealing with something real and something to track down very quickly."

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