Federal health officals now project that at least 450,000 Americans will have been diagnosed with AIDS by the end of 1993 and that as many as 100,000 new cases will be reported in that year alone.

The estimates represent the first major revisions in two years of the nation's projected AIDS caseload. And they are the first to extend the original Public Health Service figures beyond the 270,000 people expected to develop the disease by 1991.

The new projections are within the range of estimates the Centers for Disease Control had made through 1991. The new figures were presented privately last week to more than 150 senior health service officals who gathered in Charlottesville to plan the future federal response to the AIDS epidemic. Although the continued growth of the epidemic presents difficult problems for the health service, federal officials say the financial implications for the public health care system are among the most troubling.

"These numbers are making even the most reluctant members of the Reagan administration say that there has to be broader national health care to cope with AIDS," said one official who attended the conference. "With the present system these trends could mean the demise of the public hospitals in the United States."

Almost every senior AIDS expert in the Public Health Service attended the Charlottesville meeting. But because it was closed to the news media, none of those interviewed would agree to be quoted by name.

In addition to predicting the future incidence of the disease, officials attempted to address many of the epidemic's most vexing problems. Scientists presenting the most recent data on vaccine research continued to call a vaccine a "distant solution, at best."

Recent research has indicated that all those infected with the Human Immunodeficiency Virus (HIV) will develop and die of Acquired Immune Deficiency Syndrome unless an effective treatment emerges. With as many as 1.5 million Americans infected by HIV, there is enormous pressure to find a drug that can halt its deadly progression.

AZT, the only drug so far that has been approved to treat AIDS, has been shown to prolong the lives of some people with AIDS. But it has not yet proven effective in preventing the onset of the disease. Many researchers believe, however, that studies now under way will show the drug slows the spread of the virus in infected individuals.

"When that happens, we are in for a very bad day," said a senior federal scientist who attended the meeting and is well informed about drug trials. "We don't have enough AZT for a million people, and this country could not afford to pay for it if we did."

AZT can cost $10,000 to $20,000 a year per person.

Several officials also advocated increased contact tracing of infected individuals so that their sexual partners could be made aware as soon as possible of the risk.

The issue is highly controversial because most public health officials say that increased tracing without strong antidiscrimination laws would only discourage those at high risk from finding out whether they are infected.

Officials at the meeting appeared to agree that federal efforts to educate and inform racial minorities about the risks of AIDS have not been aggressive enough. Racial minorities are disproportionately represented among AIDS-infected individuals in the United States.

In addition, until recently, most drug trials have been carried out almost exclusively in populations of gay white men. Researchers at the conference stressed that not only is that unfair to racial minorities and women, but that those results may not be easily applied to other groups.

One of the strongest recommendations at the conference, one that was also sought in the report issued earlier last week by the Institute of Medicine, suggests that the terms AIDS and ARC, or AIDS related complex, are no longer useful in describing the disease.

"The disease is HIV disease," said one participant. "It starts when you become infected with the virus. And its complications continue from there. The idea that you ought to wait around until symptoms develop is ridiculous. Infected people need to know it and seek medical advice right away."

The numerical projections presented by CDC officials extend earlier estimates formulated in 1986 at a conference at Coolfont in West Virginia. The new data predicts that in 1992, 95,000 new cases of AIDS will be reported, and the following year the figure could be as high as 100,000.

Since 1981, when the disease was first described, more than 63,000 cases of AIDS have been reported to the CDC. Although the original figures from Coolfont continue to be accurate to within 5 percent of estimates, CDC officials have been wary of making strong projections because so little is known about the number of those currently infected and because the virus can lie dormant for years.

Only after Dr. Peter Fischinger, AIDS coordinator for the Public Health Service, pressed them for five years' worth of figures did CDC officials unveil an estimate that 80,000 to 100,000 new cases would be reported in 1993. Dr. James Curran, director of AIDS activities at the CDC, stressed that the estimates are preliminary and could change.