According to a study by the Centers for Disease Control and Prevention, 4.4 percent of U.S. men aged 23-29 who admitted having sex with other men became infected with HIV each year between 1998 and 2000. Infection rates varied drastically by race, with a 2.5 percent annual infection rate among whites, 3.5 percent among Hispanics and 14.7 percent among blacks. Linda Valleroy, senior author of the six-state study, likened the higher infection rate to "what's been seen in eastern and southern Africa."

"That rate means that of 100 men who are healthy at the start of a year, 15 will end up infected," Dr. Valleroy said. "These are explosive HIV incidence rates that we haven't seen since the early '90s."

Although the study is too small to indicate a national trend, "I think it gives a very good picture of what potentially could be happening in other parts of the country," said Helene Gayle, director of the National Center for HIV, STD and TB Prevention.

In the 20 years since AIDS was identified, an estimated 21.8 million people have died from the disease—including three million last year—and 36 million are believed to be infected.

More than five million people—an average of 15,000 daily— are infected each year. More than 30 experimental AIDS vaccines have been tested in humans, but none has been found effective. Margaret McCluskey, head of a vaccine study conducted by Johns Hopkins University and vaccine manufacturer VaxGen, said: "Most public health professionals agree that unless we find a definitive vaccine, which is questionable, we may not see an end to the pandemic in our lifetime. Not just an end to it. We may not even be able to control it." Even optimistic researchers caution that an effective vaccine, if it can be developed, is probably a decade away. (Source: Scripps Howard News Service, The New York Times.)