As thousands of AIDS experts, activists and politicians streamed into Toronto on Saturday for the world's largest conference devoted to combating the disease, many were determined to speak for the 2.3 million infected children who are often forgotten.

Although drugs exist to prevent a mother from transmitting the disease to her child at birth, many children, particularly in Africa, do not live to see their fifth birthday because of the viral scourge which has killed more than 25 million people in the last 25 years.

"It's intolerable," said Stephen Lewis, U.N. Special Envoy on HIV/AIDS in Africa. "It's such an indictment of the international community and of multilateral agencies, I don't know how they can hold their heads up."

Lewis blamed drug companies and apathetic governments, noting that drugs are used successfully in the West to treat and prevent the disease from birth.

"Why is the life of a Western child worth so much more than the life of an African child?" he said. "We can begin saving lives tomorrow morning."

These sensitive cultural issues, funding debates and hopeful new drug and scientific research will be on the table for some 24,000 delegates from 132 countries gathering for the 16th International AIDS Conference, which opens Sunday and runs through Friday.

Bill and Melinda Gates — flush with their $30 billion commitment from Warren Buffet to fight such diseases as AIDS — and former U.S. President Bill Clinton are among the high-profile names due to address the conference. The world's leading AIDS experts, including Lewis and UNAIDS executive director Dr. Peter Piot, are also on hand.

This year marks the 25th anniversary of the first reported cases of human immunodeficiency virus, or HIV. Since the beginning of the pandemic, nearly 65 million people worldwide have been infected with HIV and AIDS has killed more than 25 million people.

There are still an estimated 11,000 new HIV infections and 8,000 deaths every day, most of them in sub-Saharan Africa, where nearly 64 percent of those infected worldwide live today.

On the eve of the summit, details emerged about the first test of a daily pill to prevent HIV infection which gave a hint of success. The experiment, done in Africa, mainly showed that the drug Viread is safe when used for prevention.

Fewer people given the drug caught the AIDS virus than those given dummy pills, but so few in either group became infected that valid comparisons cannot yet be made, scientists said.

Still, "it's incredibly encouraging," said Dr. Helene Gayle, president of the anti-poverty group CARE and co-chair of the Toronto conference.

If future studies show effectiveness, the drug "would be an incredibly important new prevention tool that we should make available as soon as possible," she said.

A vaccine is considered the best hope for stopping the spread of AIDS, but scientists have not been able to make one that prevents infection. Condoms and counseling have not been enough.

The new approach involves Viread (known generically as tenofovir), a drug already used to treat AIDS. Animal research suggests that taking it before being exposed to HIV, through drugs or sex, could help prevent infection.

A study by Family Health International, funded by the Bill & Melinda Gates Foundation, tested it on women in Africa, many of whom were prostitutes at high risk because of multiple sex partners. After an average of six months, only two HIV cases developed among the 427 women on Viread, compared with six infections among the 432 given the fake drug.

"We really would be irresponsible to draw conclusions at this time," because those are too few cases to make judgments on, said Dr. Ward Cates of Family Health. "But it does underscore the importance of moving forward very quickly now on the other studies on the drawing board."