So many kinds of illnesses have been traced to the AIDS virus that leading researchers have concluded that the term "AIDS" no longer adequately describes the nature or magnitude of the epidemic.

They now regard acquired immune deficiency syndrome as only the most dramatic and visible form of a complicated disease and think that AIDS has become a misnomer based on symptoms rather than infection. Instead, many argue that the epidemic should be renamed after the virus that causes it: the human immunodeficiency virus (HIV).

The Public Health Servie estimates that as many as 1.5 million people have been infected with the virus, almost 30 times the number of those who have been diagnosed with AIDS. A growing body of scientific evidence suggests that most -- perhaps all -- of those infected will get sick. And recent research shows that the virus often causes serious damage even to those who seem healthy.

"It has been clear for some time that the real epidemic starts when you become infected with HIV," said William Haseltine of the Harvard School of Public Health. "AIDS is just the most severe manifestation of that disease, but there are many more and they can kill you, too."

AIDS-related complex (ARC), for example, has made tens of thousands of Americans gravely ill and has killed many others. But because the Centers for Disease Control (CDC) has established a specific definition of AIDS, those who die from ARC are not normally included in the weekly count of AIDS cases.

In addition, recent studies have suggested that HIV causes a loss of mental function long before other symptoms of AIDS surface.

As they learn the many ways HIV can assault the body, physicians have begun to disregard the official definition of AIDS, saying that they find it of little use in treating patients. Although the CDC approach remains the standard one for tracking the disease in the population, newer methods give a far better picture of the damage the virus causes.

The CDC system relies heavily on specific symptoms and illnesses associated with HIV infection for its definition of AIDS. It was established before researchers had discovered that HIV caused AIDS. And it has been modified several times in the past five years.

Last year federal officials expanded the definition of AIDS to include dementia and emaciation among the illnesses that can be caused by HIV infection.

Until then, to be diagnosed with AIDS a person would have to show evidence of a damaged immune system and the presence of at least one of the officially recognized cancers or opportunistic infections such as Kaposi's sarcoma or pneumocystis carinii pneumonia.

But Army doctors have developed a system that evaluates subtle changes HIV causes in the blood of infected people that harm key parts of the immune system. Specialists, including those at CDC, say that it does a better job of measuring the effects of the disease among individuals.

HIV slowly destroys the immune system by attacking the cells responsible for leading the body's defense against illness and in some cases by invading the central nervous system.

Under the CDC system, 20 to 30 percent of those infected with HIV will develop AIDS within three to five years of infection. But the staging system developed by the Walter Reed Army Institute of Research tells a far more alarming story.

"Walter Reed doesn't look at symptoms as much as it looks right at what HIV has done to the immune system," said Dr. Anthony S. Fauci, director of AIDS activities for the National Institutes of Health. "It shows that the vast majority {of those infected} have some deleterious effect of the virus within five years."

Researchers at Walter Reed and other medical centers around the country who have studied the depletion of the type of blood cells that protect the immune system have found that at least 90 percent of infected individuals will suffer demonstrable damage to those cells within three to five years.

That means HIV begins to cause serious damage to most infected people long before the symptoms of AIDS appear and often before people become aware they have been infected. And it suggests that treatment cannot wait until symptoms become evident.

"The CDC definition of AIDS should never be used clinically," said Dr. Margaret Fischl, director of the comprehensive AIDS program at the University of Miami School of Medicine. "It makes no sense. These are all patients who need the attention of physicians. They need tests and treatment.

"Having seen more than 2,000 patients with this illness, it drives me crazy to have people tell me it's not AIDS if it doesn't fit a CDC description."

CDC officials say that the definition of AIDS has been developed for reporting and public health purposes only. They draw a distinction between how individual patients should be treated and how the epidemic should be assessed statistically as a public health threat.

"There is nothing magic about the CDC system," said Dr. Harold Jaffe, chief of AIDS epidemiology there. "We created it for a specific purpose -- to monitor trends in life-threatening manifestations of HIV infections. As we know more about those trends, we will amend the system."

Last year's revisions raised the number of AIDS cases by nearly 15 percent and enabled thousands of people to qualify for Social Security disability payments and other benefits reserved for AIDS patients.

But for thousands of others the revisions did nothing. Federal health officials estimate that there are as many as 10 people with ARC for every one with AIDS. Many of them are without detectable symptoms. But others can be gravely ill and still not qualify for the automatic benefits that people with AIDS can get.

Because its symptoms vary so greatly, ARC is difficult for many physicians to define. Its meaning can vary greatly, and there are huge discrepancies in the use of the term. The term has never been officially recognized by CDC for reporting purposes.

"ARC really isn't a thing," said Christine Gebbie, chairman of the AIDS task force for the Association of State and Territorial Health Officers and a member of the presidential commission on AIDS. "It's a bunch of letters that happened because we could see sick people who needed to be described in some way, but they did not fit the definition of AIDS. It tells us very little about the disease. And I am sure its use will diminish as we learn more about HIV."

Because ARC can so easily be confused with other illnesses, such as hepatitis or mononucleosis, few states report it. But ARC patients often exist in a painful netherworld: They are too sick to work but cannot easily qualify for Social Security benefits.

Several studies have shown that people infected with HIV who do not yet have AIDS experience greater levels of stress and anxiety than people with AIDS. In many cases, the pressure of waiting to get sicker appears greater that that associated with the illness itself.

For a person with ARC to receive benefits, physicians must persuade the Social Security Administration that the patient has become disabled. The disease often progresses far faster than the bureaucracy can respond.

"For so long AIDS has been defined by exclusion," said Richard Dunne, executive director of New York's Gay Men's Health Crisis, the country's largest AIDS service organization. "These decisions ought to be based on disability, not on what name has been placed on your condition.

"There are many people with AIDS who work and do not need disability. But there are also thousands with ARC who need it and cannot get it. "

The elaborate systems that have been developed to describe the disease HIV causes are outmoded, according to Dr. Samuel Broder, chief of clinical oncology at the National Cancer Institute.

"The virus would certainly be shocked if it could understand how we have chosen to classify it," Broder said. "It's like people who don't want to move to a bigger house but keep building on new rooms. The place can look a little odd after a while."