For the first time in the 20-year history of the AIDS epidemic, about as many women as men are infected with HIV, a United Nations report says.

The report, presented Tuesday in London, paints a dismal picture of a disease invading regions of the globe where it had for many years tricked experts into believing some populations might be less susceptible, or even immune, to infection.

"It's once more a sad story -- 42 million people living with HIV today, 5 million new infections in 2002 and 3.1 million [who have] died from AIDS this year," said Dr. Peter Piot, executive director of the U.N. aids agency.

The report said 38.6 million adults and 3.2 million children under age 15 have HIV. Of the adults, 19.2 million are women.

The virus is spreading most rapidly in eastern Europe, where nearly every country is experiencing a major outbreak. It has also marched swiftly across Central Asia and into China, where it was almost nonexistent a few years ago.

But there are signs of hope. The AIDS Epidemic Update, an annual report by the World Health Organization and UNAIDS, says prevention programs appear to be working in the few areas where they have been set up.

"There are a number of countries where we have strong empirical evidence that rates of infection are declining, and in each case they are declining among young people," Piot said.

He cited South Africa, where HIV infections among pregnant teenage girls fell 25 percent between 1998 and 2001. In Uganda, the number of new HIV infections has been dropping every year for the last 10 years, he said.

"This positive trend is the first signal that there is an impact of the prevention and education programs," Piot said.

Overall, though, there is not only an increase in the sheer number of people being infected, but also an increase in the number of countries now facing epidemics, said Dr. Bernhard Schwartlander, director of the HIV/AIDS division at the World Health Organization.

For example, 10 years ago HIV was confined to small areas of Eastern Europe. Today, every country in the region has an HIV problem.

"We have seen that no society is immune," Schwartlander said. "Even though HIV was quite well established in many Asian countries very early on, we had seen a very stable low rate in a number of countries. It was just at the point in time where people were starting to think maybe these societies are immune. We have been shown different."

"In Indonesia, after many years of silence, of very low rates," an epidemic is growing, Schwartlander said. "Of course HIV was there, but it didn't really lead to major epidemics. It was just over the past couple of years that massive spread of HIV has begun, initially in injecting drug users."

In China, where HIV was "virtually nonexistent" a few years ago, there are now 1 million people with HIV, and the number could well rise to 10 million by the end of the decade, he said. Again, drug use is a major factor.

Sub-Saharan Africa is still by far the worst-affected region. The situation there also reflects the spread of AIDS among women, with about twice as many young women as men infected.

In 2001, 6 percent to 11 percent of women between the ages of 15 and 24 years old had HIV, compared with between 3 percent and 6 percent of men in the same age group.

It is particularly difficult for women in this region to take precautions against HIV because of their subordinate position in society. Rape is common in some countries.

The phenomenon of intergenerational sex is also driving much of the epidemic in southern Africa, where between one-quarter and one-third of older men are HIV positive.

A recent study found that in Zimbabwe, for instance, many adolescent girls have sex with men in return for clothes and money for school fees.

Piot said the shift toward women will ultimately exacerbate the spread of HIV, because they can spread it not only through sex, but also through nursing and childbirth.

While HIV drugs can prevent the virus from being transmitted through nursing, few women in Africa have access to them.

The report also found that the HIV epidemic is aggravating the famine in sub-Saharan Africa, where it is women who work the fields.

"This is the first large-scale sign of what the impact of AIDS can and will be for society as a whole," Piot said.

Alan Whiteside, director of the Health Economics and HIV/AIDS Research Division at the University of Natal in Durban, South Africa, said it is clear that AIDS is not just a health crisis, but also a development crisis.

The virus is causing an economic crisis in southern Africa, he said, and worsens political crises in places such as Zimbabwe.

"In a situation where life expectancy has plummeted it's very hard to keep them engaged in a future when they don't believe they have one," Whiteside said.