While the war against HIV/AIDS is still far from over, 2009 could prove to be a watershed year in terms of advances in prevention and treatment, experts say.

The view on this World AIDS Day, Dec. 1, does seem a bit brighter. In fact, just last month a United Nations report found that the number of people infected with HIV globally has remained unchanged, at about 33 million, for the past two years, and may have peaked in the late 1990s.

Why the change? One big reason could be expanded access to antiretroviral drugs. A report released in October by the World Health Organization, UNICEF and UNAIDS found that 42 percent of people in the developing world who carry HIV now have access to life-extending medications. By the end of 2008, more than 4 million people worldwide were on antiretroviral medicines - 2.9 million of them in sub-Saharan Africa, where the bulk of HIV-positive people live. That's a tenfold increase in access over the prior five years.

"I think this has come about through a number of organizations that have been trying to get drugs to be available to people in the developing world," said Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases. He especially credited the President's Emergency Plan for AIDS Relief (PEPFAR), begun under the second Bush presidency, which he said "is responsible for over 2 million people being on therapy."

Other nonprofit groups - most notably the Clinton Foundation and the Gates Foundation - have also led the charge, helping to broker price-reduction schemes with pharmaceutical companies for the cheap distribution of AIDS drugs in poorer nations.

More widespread access to treatment may also pay dividends in prevention, one expert noted.

"I think this is an interesting story that's been emerging this year, as well - the possibility that people who are on antiretroviral therapy are less infectious," said Rowena Johnston, director of research for the Foundation for AIDS Research (amfAR), based in New York City. She said that while the effect of widespread treatment on infectivity has yet to be proven, decreased viral load in infected people might help reduce the odds of their passing HIV on to others.

In fact, the U.S. Centers for Disease Control and Prevention and the U.S. National Institutes of Health are planning major studies in New York City and Washington, D.C., to see if better identification and treatment of HIV-positive people can help keep infection rates down across the community as a whole, Johnston said.

There was also promising news this year in terms of the search for an effective AIDS vaccine.

In October, researchers reporting in the New England Journal of Medicine confirmed that a combination of two vaccines brought about a modest, 31 percent reduction in infection rates among a cohort of 16,000 young adult volunteers in Thailand who were tracked for about three years. Analysis of the trial data suggested that the vaccines' effect faded with time, however, and was less effective in those at highest risk of HIV, such as sex workers or IV drug abusers.

For these reasons, no one is calling the trial a success. However, "the reason that we think it is potentially important is that it's the first time that we've ever seen the slightest positive signal" that immunization against HIV might work, Fauci said. "So, mild as [this result] is, at least it's a step in the right direction."

Johnston agreed, and called the trial an important stepping stone to further research.

"There's going to be a lot of intensive effort looking at blood samples of the people who seem to have done well on the vaccine," she explained. "If anybody can tease out what the magic ingredients are, that will form the cornerstone of how we move forward on AIDS vaccine development."

There were also new glimmers of hope in terms of treatment. One major story was reported as a case study in February in the New England Journal of Medicine. The patient in question was both HIV-positive and had leukemia, and received a stem cell transplant to help cure the cancer. The transplant was unique, however, in that the donor carried a rare gene mutation providing virtual immunity to HIV.

The result: post-transplant, the patient now has no detectable level of HIV in his system.

Johnston stressed that such a therapy could never become a widespread treatment for HIV/AIDS, because the donor pool is so scarce and bone marrow transplants carry a 30 percent risk of death. But the case does offer intriguing possibilities.

"It's a proof of concept that maybe you can cure HIV," she said. "So, there's been interest in finding out where you could do something similar with using gene therapy, for example," bypassing the need for dangerous stem cell transplants.

Other advances in HIV/AIDS made headlines as well in 2009. In February, a topical microbicide gel was found to cut the odds of HIV infection in at-risk African women by 30 percent, while in September researchers at the International AIDS Vaccine Initiative said they'd discovered two immune-system antibodies that might become powerful, broad-spectrum targets for vaccine research in the future.

And in policy news, the Obama administration in late October lifted a decades-old ban on foreigners with HIV entering the United States. As reported by the Associated Press, Obama described the ban as a policy "rooted in fear rather than fact," and said its removal would encourage HIV testing and help save lives.

Still, despite this year's advances, HIV/AIDS continues its decades-long swath of destruction, both in the United States and globally.

As Fauci pointed out, the annual rate of new infections in the United States has been stuck at a dismal 56,000 for the past decade. "We've sort of hit a wall to get below that number," he said. "We need to intensify the multifaceted prevention efforts that are ongoing."