Lifesaving drugs known as antiretrovirals that have brought millions of AIDS sufferers back from the brink also dramatically cut the risk that they will transmit the virus to their loved ones - by as much as 96 percent.

The landmark study, known as the HIV Prevention Trials Network 052 trial, proved that AIDS treatment was also a powerful form of prevention. Science magazine dubbed it the 2011 Breakthrough of the Year.

The findings - along with studies on the preventive benefits of circumcision and treating high-risk individuals before they are exposed to HIV - have been heralded as weapons that could finally break the back of the AIDS epidemic.

"What was unthinkable just three years ago is now in sight: an AIDS-free generation and the end of this epidemic," Ambassador Mark Dybul, former U.S. Global AIDS Coordinator for President George W. Bush, said at the 2012 International AIDS Conference in July.

But fully rolling out treatment as prevention would mean more than doubling current HIV treatment goals, from the current United Nations target of treating 15 million by 2015 to 34 million, a staggering increase.

With some recession-strapped donor countries already struggling to meet their current commitments for treatment and prevention programs, AIDS activists worry that money, and not science, could hold up progress in the war on AIDS.

EARLIER TREATMENT GAINS TRACTION

"The benefits of early detection and treatment have never been more clear, but countries have never been more challenged to provide needed resources," Kaiser Family Foundation Chief Drew Altman said in a statement.

Total funding for HIV prevention, care and treatment has been flat for the past three years, as countries balance the needs of their own struggling economies with their commitment to fighting AIDS.

Funding for low- and middle-income countries totaled $16.8 billion last year, the latest United Nations figures show. Rich donor nations provided $8.2 billion of that sum, nearly half from the United States.

An analysis by Kaiser and the United Nations found that United States and Britain - the two biggest donor nations - increased funding in 2011 over 2010. Australia, Canada, Denmark, France, Germany, Norway and Sweden flatlined funding, and Ireland, Italy, Japan and the Netherlands made cuts.

"The funding environment is very tough," billionaire philanthropist and Microsoft Corp co-founder Bill Gates said at the AIDS conference last month.

"Some days it feels like we're going to have to fight just to keep the funding at the level it's at today, and yet we need to put new patients on treatment."

One bright spot is that poor and middle-income countries increasingly are stepping up, according to the United Nations.

In 2011, low- and middle-income countries spent $8.6 billion last year on HIV/AIDS - the first time such nations have outspent rich donors. Ghana, Kenya, Nigeria and South Africa, as well as China and India, increased domestic spending on AIDS.

Altogether, that $16.8 billion helped cover HIV treatments for 8 million people in middle- and lower-income countries, up from 6.6 million in 2010. But that is still $7.2 billion a year short of what the United Nations says it needs to reach its goal of treating and caring for 15 million infected individuals by 2015.

That goal reflects World Health Organization recommendations that those diagnosed with HIV should start treatment when their infection-fighting cells fall below a certain level, a sign that their immune system is weakening.

But the 052 prevention study, which involved 1,763 couples across Africa, Asia and the Americas, argues for earlier treatment, before their immune system begins to fail.

"The study demonstrates tremendous benefit in early and probably immediate treatment of people who are tested positive for HIV, before their health is compromised, to render them non-infectious as well," said Dr. Myron Cohen, an HIV/AIDS researcher at the University of North Carolina and leader of the trial.

The findings, published in August 2011 in the New England Journal of Medicine, made clear the need for a major expansion of treatment.

Nearly a year later, the World Health Organization recommended 'strategic use' of antiretrovirals, saying they should be offered to HIV-infected individuals with uninfected partners, to pregnant women and to high-risk populations, regardless of their immune status.

Those changes would increase the number of people eligible for treatment from 15 million to 23 million, WHO said.

That is still short of recommendations for treating all HIV-infected individuals, a position backed earlier this year by both the U.S. Department of Health and Human Services and the nonprofit International Antiviral Society-USA. WHO said it is considering universal treatment based on the findings, something Cohen thinks is ultimately inevitable.

"You will have several years to ratchet up, but if there are 34 million people who are infected, there are 34 million people who need to be treated," Cohen said.

"We might as well just accept that."

'SELLING' PREVENTION

For donor nations and resource-poor governments to embrace that new reality, however, it may take a lot more proof.

One hesitation is that the drugs work so well that people who take them can live basically a normal life, which means countries are on the hook for a lifetime of treatment.

"It frightens people," Cohen said. "They squirm and say, 'Oh my god; 34 million people for 50 years on these drugs. It's impossible.'"

In 2000, the annual cost of antiretroviral treatment was $10,000, leading donor nations to talk about "treatment mortgages." Now, greater access to generics has cut the cost of treatment to less than $100 a year for the least-expensive WHO-recommended regimen.

But HIV patients often develop resistance to first-line therapies, forcing patients to move to more costly treatments to keep the virus under control.

Dr. Brian Williams, a Geneva-based epidemiologist at the South African Centre for Epidemiological Modelling and Analysis, said many modeling studies suggest that universal treatment would be cost effective. He estimates overall costs for antiretroviral treatment at $500 per patient per year, putting the annual cost of treating 30 million HIV-infected individuals at roughly $15 billion.

Those figures do not include other HIV prevention efforts, nor do they include the cost of testing and caring for HIV-infected individuals.

Even so, Williams says it is feasible.

The challenge is trying to sell the prevention aspect of treatment as cost-effective.

As Williams put it: "The science is the easy bit. The politics is the hard bit."

Dr. José Zuniga, president of the International Association of Physicians in AIDS Care, said scientific advances have raised hope for an end to AIDS, but researchers need to temper that with the reality that it will be tough to translate the science into the potential benefit "without some heavy lifting." That includes making strong, fact-based arguments that help people think beyond the near-term.

In addition to treatment as prevention, Zuniga sees promise in studies showing that giving antiretrovirals to healthy people at high risk of HIV-infection can slow transmission, although many questions remain about this approach, called Pre-Exposure Prophylaxis or PrEP.

HIV/AIDS experts will test these efforts - along with less costly approaches, such as counseling, condom use and circumcision - in as many as 50 studies globally to see how well they work in real-world settings.

Dr. Sten Vermund of the HIV Medicine Association and an HIV/AIDS researcher at Vanderbilt University in Nashville, calls this "operational research."

He is part of a U.S.-backed trial that will study a combination of testing, counseling and early antiretroviral therapy among different populations in Zambia and South Africa.

Another study by Johns Hopkins will look at prevention strategies in Tanzania, and a third from Harvard will study prevention strategies in Botswana.

"While we believe the more people we treat, the more benefit we'll see, we are trying to prove that to ourselves so we can weigh the benefit at the public health level," Cohen said.

Cohen says he appreciates the strain that vastly expanding HIV treatment will place on health systems, but he thinks countries "should not look at it as a commitment forever."

Instead, he sees it as a bridge to the next big breakthrough, and he calls on funding agencies to redouble their research efforts in finding a vaccine or even a cure, which would hasten the end of the epidemic.

Cohen draws on the past for proof, noting that in 1985, 14 percent of all patients admitted to his hospital in North Carolina were infected with HIV.

"They all died."

Ten years later, Cohen was caring for a young woman whom he thought would die. She started taking AZT, the very first HIV drug. When she returned to the hospital later for a minor hand infection, she had gained 20 pounds.

"It was the most amazing thing I'd seen in my career."

Having witnessed that, Cohen said, "I wouldn't be very surprised to see something else tremendously different in 2025."

(Editing by Michele Gershberg and Mary Milliken)

• A Permanent Economic Emergency