By John Donnelly, Globe Staff, 7/7/2002

BARCELONA - AIDS is striking the world's poorest young women with stunning ferocity, according to United Nations figures showing that infected girls and young women in sub-Saharan Africa outnumber infected young men by 2 to 1.

Of the region's 8.6 million people between the ages of 15 and 24 who have the disease or the virus that causes it, 67 percent are women and girls. In South Asia, young women make up 62 percent of the cases, according to reports by UNICEF and UNAIDS.

The figures, though startling in their revelations about the health risks for women in the developing world, were not highlighted by UNAIDS in its recent global report on the epidemic and instead were culled from tables in the back pages of the overview. Overall, an estimated 15 million women in sub-Saharan Africa were infected, or 58 percent of all cases there.

''When I saw those numbers I thought to myself, `Good grief, what will happen to the women of Africa?''' said Stephen H. Lewis, UN Secretary General Kofi Annan's envoy on AIDS in Africa. ''It's an unbelievably horrifying pattern.''

As the 14th International AIDS Conference opens in Barcelona today, Lewis and other global health experts say that the plight of young women has slipped out of the limelight in recent years and needs to be urgently addressed this week and beyond by leaders in Africa, South Asia, and wealthier countries.

In 1990, health experts estimated that women and men in sub-Saharan Africa were equally infected with HIV, totaling 3 million cases. Today, 28.5 million people are infected with the virus in the region.

People between ages 15 and 24 make up about one-quarter of all those infected worldwide, but that percentage is about to increase rapidly.

UN epidemiologists say that half of those newly infected today are in that age range, considered the most sexually active group.

In the United States, Latin America, the Caribbean, the Middle East, and Russia, boys and men ages 15 to 24 are infected in higher numbers than young women. But those regions have less than a quarter of all young people infected, according to the studies.

The reason, according to AIDS experts, is that three-quarters of all cases in the world are now transmitted through heterosexual relations - up from 60 percent in 1990.

Women are physiologically more susceptible to contracting the virus through vaginal intercourse. Men are eight times more likely to transmit HIV to women than women to men because of the biology of the vagina - the tissues are thinner and break more easily in younger women - and because of semen's effectiveness as an HIV transmitter.

Another major reason for the lopsided gender figures is that dire economic straits often force young women into prostitution or marriages with older men, who are more likely to be infected.

In industrialized regions of the world and most areas of Latin America and Russia, the disease is widely transmitted by men having sex with other men or through shared needles by intravenous drug users. Today, the number of men infected in the United States outnumbers women by 2 to 1.

The UNICEF report, ''Young People and HIV/AIDS,'' was based on information from 60 countrywide studies, and a section was devoted to the vulnerability of girls.

''Young girls living in poverty are often enticed or coerced into having sex with someone older, wealthier, or in a position of authority, such as an employer, schoolteacher, or older `sugar daddy,' in order to stay in school or support themselves and their families,'' the report said.

A study in Botswana found girls as young as 13 who do not attend school had sex with older men. About one in five of those not in school said it was difficult to refuse sex when money and gifts are offered.

At the end of the UNAIDS and UNICEF reports, tables showing figures for each country detailed the disparity of cases between women and men in the most sexually active age group.

Using the higher end of the estimates, the report found:

In Lesotho, the percentage of young women with HIV or AIDS was 51 percent, while the rate for young men was 23 percent; in Botswana, young women were at 45 percent, young men at 19 percent; South Africa, 31 percent to 13 percent; Swaziland, 47 percent to 18 percent; and Zambia, 25 percent to 10 percent.

Compounding the problem, according to the reports, young women in many countries know little about AIDS, including how it is transmitted and how it can be prevented.

In Nigeria - the most populous nation in Africa and a country very likely to have a large explosion of AIDS cases, according to US National Intelligence Council analysts - 95 percent of the young women perceived their risk of contracting AIDS as minimal to nonexistent. More than 80 percent of girls and young women ages 15 to 24 did not have good knowledge about sex in Cameroon, Central African Republic, Equatorial Guinea, Lesotho, and Sierra Leone.

The age at which young women first have sex also was seen as a major problem, the reports said. In Ethiopia, 14 percent of the women surveyed said they had had sex before age 15, while the figure in Nigeria is 17 percent. The two countries have a combined population of 180 million, and, Lewis said, ''stand at the very precipice of an explosion in the pandemic.''

''When you see the level of sex initiation in societies, clearly some major new work needs to be done about changing cultural norms,'' said Todd A. Summers, president of Progressive Health Partners, a Washington-based consulting firm.

Geeta Rao Gupta, president of the International Center for Research on Women, a Washington advocacy group that seeks to improve the lives of women in poor countries, said HIV infection rates among women ''were talked about a lot five to seven years ago, but it wasn't followed through with action.''

''The numbers keep going up and are very scary now,'' she said. ''The vulnerabilities have been known but not really absorbed by the leadership at the country level and community level.''

Lewis said that in his year traveling around Africa as Annan's representative, women have constantly asked him for help.

''Women are the backbone at the village level. They are the people who do all the caring,'' said Lewis, a former Canadian diplomat who was deputy executive director of UNICEF from 1995-1999. ''It's a form of conscripted labor. Women have no alternative but to look after the dying people around them.''

He said that these two realities - women holding together families and young women infected in much higher numbers than men - meant that the focus of the fight against AIDS must fundamentally shift to save them.

''The world has to understand it. AIDS is effectively becoming a war on women.''

John Donnelly can be reached at donnelly@globe.com