A global medical forum on AIDS got down to business on Sunday for four days of debate on powerful new weapons to combat a pandemic that in 30 years has claimed as many lives as a World War.
Held every two years, the meeting is taking place in Rome amid a flurry of startlingly good news from field trials, prompting some veterans to talk of a watershed in the AIDS story.
"This conference could well be a turnaround," Elly Katabira, president of the International AIDS Society (IAS) staging the meeting, told a press conference.
"The results presented this week could prove today as important as the antiretrovirals breakthroughs of the mid-nineties."
The cause for the excitement is scientific proof that the famous "cocktail" of drugs used to treat people with the human immunodeficiency virus can also be used to prevent HIV infection in others.
The conference will hear the latest data from a trial conducted among "sero-discordant" heterosexual couples in Africa, meaning couples in which one partner had been tested positive HIV while the other was uninfected.
The risk of HIV infection fell by 96 percent when the infected partner started early use of daily antiretrovirals.
Evidence of this kind -- supported by several other trials in which treatment drugs were used for prevention -- points to new ways to stop the relentless rise in new HIV infections, say some experts.
Thirty million people have been killed by AIDS since the disease first came to light in June 1981. In 2009, more than 33 million people were living with HIV and 2.6 million people became newly infected, according to UNAIDS.
"We have the proof: this really is a landmark moment in prevention, it is a revolution in a sense," said Stefano Vella, research director at Italy's Superior Institute of Health.
Asked if the end of the pandemic was in sight, Chris Beyrer, a professor at the John Hopkins Bloomberg School of Public Health in Baltimore, Maryland, said "the chances just got tremendously better."
But funding and turning the scientific evidence into action on the ground were the key, he cautioned.
AIDS spending today is around $16 billion (11 billion euros) annually, compared with current needs estimated at 24 billion, said Michel Sidibe, executive director of UNAIDS.
"Treatment as prevention could pay for itself in about a decade," Jean-Paul Moatti, an economics professor at France's University of the Mediterranean in Marseille, southern France, told AFP.
"Countries would have lower health costs and better productivity because fewer people fall sick."
The conference gathers 5,500 specialists, ranging from virologists to pharmacologists and disease trackers.
It is staged once every two years by the IAS, which also organises the International AIDS Conference, a bigger event that touches on the pandemic's many social dimensions.
Other trials to be discussed in Rome will look at the effectiveness of giving uninfected people HIV drugs -- an approach called "pre-exposure prophylaxis," or PrEP -- and progress to encourage circumcision in African men. Male circumcision has been found to more than halve the risk of HIV infection for men.