TORONTO -- Bill and Melinda Gates, whose foundation has contributed $1.9 billion to fight AIDS, said Sunday that the search for HIV prevention drugs that would empower women could be the "next big breakthrough" in combating the disease.
The couple joined more than 24,000 scientists, activists, celebrities, HIV-positive people and humanitarians from 132 countries for a conference on how to combat the disease that has killed 25 million people since the first case was reported a quarter of a century ago.
Gates, who recently announced he would step down from his day-to-day duties at Microsoft Corp. and devote more time to philanthropy, said the search for a vaccine to prevent the virus that causes AIDS was the foundation's top priority.
The Bill & Melinda Gates Foundation has given $1.9 billion to support HIV/AIDS projects worldwide since 1995 and announced last week a $500 million grant to the Global Fund to Fight AIDS.
"We want to call on everyone here and around the world to help speed up what we hope will be the next big breakthrough in the fight against AIDS -- the discovery of a microbicide or an oral prevention drug that can block the transmission of HIV," Bill Gates said at the opening ceremony of the 16th International AIDS Conference.
"This could mark a turning point in the epidemic, and we have to make it an urgent priority," he added.
Microbicides are gels or creams women can use to block infections and disease. Sixteen microbicides are being clinically evaluated; five are in major advanced studies.
The couple called for greater advocacy to break the stigma of AIDS for women in impoverished nations who typically have little say over their own sex lives or health.
"We need tools that will allow women to protect themselves," Bill Gates said. "This is true whether the woman is a faithful married mother of small children, or a sex worker trying to scrape out a living in a slum. No matter where she lives, who she is, or what she does -- a woman should never need her partner's permission to save her own life."
Melinda Gates said the couple visited an AIDS hospice in southern India last December and noticed the wards were divided by gender; the male ward filled with families and flowers.
"Across a courtyard, we saw a very different scene," she said. "The female ward was a lonely, desolate place. There were no visitors, just women wasting away from AIDS. There was no love, no warmth, no comfort. Just wives, daughters and mothers, left alone to die."
"Stigma is cruel," she added. "It is also irrational."
The United States is often harshly criticized for not doing enough to help poorer countries fight AIDS or demand U.S. drug companies to lower the cost of AIDS drugs. But Gates praised U.S. President George W. Bush for his pledge of $15 billion over five years to combat the disease in 15 countries in Africa, Asia and the Caribbean, noting it was the largest single pledge ever made to fight a disease.
Other opening ceremony speakers included actor Richard Gere and pop singer Alicia Keys, who marched across the city earlier with several hundred African and Canadian grandmothers to show their support for the elderly women in sub-Saharan Africa forced to take care of their grandchildren after their own children had died.
It is estimated that 13 million children in sub-Saharan Africa have been orphaned by AIDS.
Also attending the conference are former President Bill Clinton, as well as international AIDS experts such as Dr. Peter Piot, founder and executive director of UNAIDS and Stephen Lewis, the U.N. envoy for HIV/AIDS in Africa.
Piot -- a microbiologist who launched the first international project on AIDS in Congo in the 1980s -- told a youth congress earlier in the day that older men hold the key to ending the scourge.
"The toughest job in HIV prevention that we have is to make older men change their behavior," Piot said, referring to men who have multiple sex partners, then pass along HIV to their wives, girlfriends or boyfriends through unprotected sex.
"The future of this epidemic is in our hands," he said. "As long as we don't change our behavior and put girls and women at risk, again, it's not going to work."
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 have been infected with HIV and AIDS has killed more than 25 million people.
Today, an estimated 40 million people are living with HIV, some 7 million more than the entire population of conference host, Canada.
16th International AIDS Conference: www.aids2006.org