A global AIDS forum was getting underway here on Sunday, with major announcements expected over six days on the drugs that have turned HIV from killer to a chronic but manageable disease, and the quest for a virus-thwarting gel.
Overshadowing the long-awaited meeting, though, are renewed worries on raising billions of dollars to help sustain the war on a nearly 30-year-old epidemic.
Thousands of scientists, policymakers, grassroots campaigners and activists flooded into the Vienna congress centre for pre-conference seminars ahead of a ceremonial start in the evening.
The global confab is set to catapult anti-HIV drugs, known as antiretroviral therapy (ART), to a new level of importance.
Around five million people around the world are alive today thanks to this therapy, which emerged in 1996 and initially was so expensive that it was restricted to rich nations.
In one of the first presentations, a panel of US scientists issued recommendations on Sunday for earlier use of ART, saying patients treated before their immune system is badly damaged by the human immunodeficiency virus (HIV) faced a lesser risk of death and sickness.
On Tuesday, researchers unveil the results from a South African trial where women volunteers tested a prototype anti-HIV gel.
The search for a vaginal microbicide has been one of the most daunting challenges in the history of AIDS.
The goal is to provide women, especially those in sub-Saharan Africa, where two-thirds of the world's HIV infections occur, with a means other than the condom to protect themselves against the pathogen.
Meanwhile, worries about money - an issue that went into retreat in recent years - are returning, say veterans of the war against AIDS.
This year, 25 billion dollars has to be mustered for fighting AIDS in poorer countries, according to a UNAIDS estimate. So far, there is a funding shortfall of 11.3 billion, according to an analysis published last week in the US journal Science.
That means a 2006 vow by UN members to provide "universal access" to HIV drugs, prevention, treatment and care by the end of 2010 is set to become one more headline-making political promise that fell flat.
Kevin Frost, chief executive of a major US NGO, Amfar, said there were signs traditional donors were "flatlining" in financial support at a time when funding needed to rise to treat the always-rising number of infected people.
Increasing costs, coupled with the need in many countries to tighten belts, are stirring a sense "just short of panic," Frost told AFP.
"I get the sense that they're saying, 'we didn't know what we were getting into'" by committing to support lifelong treatment, he said.
The Vienna meeting, for which 20,000-25,000 people have registered, is the 18th International AIDS Conference. The meetings are held every two years.
Other major issues at the meeting include the situation in Eastern Europe and Central Europe, where the pandemic is accelerating, especially among intravenous drug users, and the theme of human rights.
VIPs include former US president Bill Clinton and Microsoft philanthropist Bill Gates, both rostered to speak on Monday, as well as rock star Annie Lennox, who will stage a concert on Tuesday.
Acquired immune deficiency syndrome (AIDS) has claimed more than 25 million lives since the disease first came to light in 1981, a toll that oustrips the fatalities of World War I.
At least 33 million people are living with the human immunodeficiency virus (HIV), a microbe that causes AIDS by destroying the immune system and exposing the body to opportunistic disease. The tally of new infections is rising by around 2.7 million a year, according to UN figures for 2008.