"Today we add another miracle to the long honor roll of American medicine and science," announced the secretary of Health and Human Services. "Today's discovery represents the triumph of science over a dreaded disease. Those who have disparaged this scientific search-those who have said we weren't doing enough-have not understood how sound, solid, significant medical research proceeds."

It was April 23, 1984. Almost 2,000 Americans were dead of AIDS. More than 100 new cases were being reported every week. For the first time since the plague began, the government was offering shreds of hope to the dying: The virus causing the disease had been isolated. An end to the nightmare was finally in sight: Within six months a blood test would be available, Heckler said; within two years a vaccine would be ready for testing.

As Heckler made her dramatic appearance on national television, Dr. Peter Duesberg sat in his cluttered office in Berkeley, Calif., bewildered. Duesberg is one of the world's foremost authorities on viruses. He was the first person to map all the different gene strands that make up a retrovirus, the very type of clever, hard-to-fight bug Heckler said was causing AIDS. To Duesberg, Heckler's announcement just didn't make sense. If her HIV virus was indeed the cause of AIDS, it violated the laws of virology. He decided to withhold his applause and wait for the proof.

Six years and 90,000 deaths later, he's still waiting. And there is still no vaccine.

In the six years since Margaret Heckler's surprise announcement, the federal war against AIDS has become a desperate $3 billion-a-year battle against HIV, Human Immuno-deficiency Virus. In the most intensive disease hunt in the history of mankind, scientists have cross-sectioned and spliced HIV. They have cultured, activated and mapped it. They have figured out how it reproduces. They can draw you a picture of it. But they are missing one important piece of the puzzle:

"We do not yet know how HIV causes AIDS," Dr. John Coffin of Tufts University, a member of the international committee that named the virus, told the delegates to the Sixth International Conference on AIDS last June.

It is that missing link that nags at a growing number of the world's best-known scientists. They have begun to suggest a frightening explanation: HIV alone may not cause the disease. Or it may have nothing to do with it.

The Doubters

By 1987, three years after the HIV discovery was announced, retrovirologist Duesberg's doubts had hardened into a certainty that something was wrong. For one thing, the numbers weren't adding up. Each year since Heckler's announcement, the federal Centers for Disease Control has projected the number of people expected to turn up with the HIV infection. Initially, scientists were confident their projections would prove accurate: They knew from years of experience how quickly a toxic new virus spreads in a human population. But, the predictions were wrong. At the end of each year, the CDC was forced to revise its estimates downward dramatically. In 1986, for example, the CDC estimated that 1 million to 1.5 million Americans were infected with HIV. A year later, they cut that estimate in half. HIV is not spreading at anywhere near the rate expected of a newly introduced sexually transmitted virus. Why? No one knows.

There were other nagging problems with the HIV hypothesis:

• Two healthy people can have sex with the same HIV-infected person, and one of them will come down with the infection after a single encounter, while the other will still not have it after 500 encounters. Why? No one knows.
• The vast majority of those known to be HIV-infected remain healthy for years-and there is no proof that they will not live a normal life span. Why? No one knows.
• Diseases presumed to signal AIDS are cropping up in individuals without any trace of HIV. Why? No one knows.
• How could a virus found to be active in only minute quantities in the bodies of even the sickest AIDS patients devastate the immune system as HIV purportedly does? No one knows.

While most researchers say such apparent contradictions are to be expected in the early stages of research into a new disease, others aren't so certain.

"There are too many shortcomings in the theory that HIV causes all signs of AIDS," says Luc Montagnier.

In June, when Montagnier, a French AIDS researcher announced his rejection of the established theory, he should have provoked a sensation. After all, Montagnier discovered HIV in the first place.

Montagnier now believes that HIV is "a peaceful virus" that becomes a killer only when combined with another bug-a bug he has already isolated and identified. This finding received none of the attention of his original discovery. The same reaction-which is to say no reaction-had greeted

Robert Gallo, Montagnier's American co-discoverer of HIV, when he also suggested in print two years ago that HIV might need a co-factor to cause AIDS. Now Gallo does not even discuss the matter.

Montagnier, however, persists-and has discovered what earlier dissenters have found out over the years: It's no fun to challenge the common wisdom.

Peter Duesberg, the retrovirologist, has been likened to obsessives who believe AIDS has extraterrestrial origins. He is, CDC researcher Harold Jaffe and his British colleague Robin Weiss wrote recently in a British science magazine, "a flat-Earther bogged down in molecular minutiae and miasmal theories of disease."

Two other dissenters, Robert Root-Bernstein, winner of a MacArthur "genius grant," and Shyh-Ching Lo, director of AIDS pathology at the Armed Forces Institute of Pathology, have been accused of quackery and endangering the public health of the nation by key AIDS policy makers for their insistence that HIV is not the sole cause of AIDS.

Even when they present evidence that their dissent might be justified, nothing happens. Montagnier was not the first one who found a second organism that may be essential to produce AIDS. A year ago this month, the National Institute of Allergy and Infectious Disease-the agency in charge of the war on AIDS-convened a panel of scientists to examine Shyh-Ching Lo's discovery of an extremely toxic micro-organism in AIDS patients. When the organism-the same mycoplasma that Montagnier would report four months later - was injected into experimental animals, the animals quickly sickened and died. That does not happen with HIV. Panel members quizzed Lo for three days, and

concluded that he was onto something important.