DURBAN, South Africa - Roughly 5 million Americans have sex and drug habits that put them at a high risk of catching AIDS, according to new U.S. figures, and experts fear an upsurge of the disease after a decade of stability.
While AIDS infections in the United States have fallen dramatically since their peak in the 1980s, public health officials worry that complacency about the disease has caused backsliding - especially among young gay men - that could bring AIDS roaring back.
''I'm scared by the trends we are starting to see,'' said Dr. Helene Gayle, AIDS chief at the U.S. Centers for disease Control and Prevention.
Gayle presented the latest data Saturday at a briefing hosted by the American Medical Association on the eve of the 13th International Conference on AIDS.
Currently, about 40,000 Americans contract HIV each year, down from the 100,000 new infections annually during the mid-'80s. The improvement is attributed largely to safer sex habits and avoiding dirty needles.
In an attempt to see how many Americans still act recklessly, the CDC analyzed findings from several large-scale surveys. Their conclusion: Between 2 percent and 4 percent of the adult population - 4 million to 5 million people - still put themselves at high risk. This includes having six or more sexual partners annually, having sex with someone known to be infected with HIV, engaging in prostitution for drugs or money, having male homosexual contact, using crack cocaine or injecting drugs.
Gayle said the study did not attempt to learn whether this level of risky behavior is increasing or decreasing, although there seems to be evidence on both sides. For instance, condom use has increased substantially since the 1980s, although only about 40 percent of unmarried people and 23 percent of drug users report using them.
Over the last decade, infection rates among gay men have remained stable at between 1 percent and 4 percent. However, said Gayle, ''We have seen troubling signs over the past year that we fear could signal a resurgence of the epidemic among gay men.''
Last week, the San Francisco Department of Public Health reported a sharp increase in new HIV infections between 1997 and 1999. Also, gonorrhea and other sexually spread diseases have risen recently in several cities among HIV-infected gay men.
Experts worry that complacency about getting AIDS, fueled in part by the availability of effective HIV treatments, may be behind a return to risky sexual behavior.
One of the most impressive victories over HIV in industrialized countries has been the use of AZT and other drugs to prevent the spread of the virus from infected mothers to their babies during birth. In the United States, only a few hundred babies now get the infection this way each year.
Many hope the same approach will slow the spread of HIV to babies where this tragedy is common, especially in sub-Saharan Africa.
On Friday, Boehringer Ingelheim said it would offer its AIDS drug nevirapine free to developing countries to help stop mother-to-child spread of HIV. However, a study scheduled to be released later at the meeting suggests this approach may not have a big impact, because infected women can still spread the virus to their babies through breast feeding.
A study of 1,797 pregnancies found that a combination of the drugs AZT and 3TC cut the risk of transmission to newborns by more than half. However, as babies caught the virus through breast milk, the difference was nearly wiped out within 18 months.
''We need to look at how to make breast feeding safer,'' said Dr. James McIntyre of South Africa's Chris Hani Baragwanath Hospital. Possibilities include weaning babies after six months, avoiding mixing breast milk with other liquids and giving anti-AIDS drugs to nursing babies.