World AIDS Day and the challenges it highlights (Christine Courcol)

As World Aids Day is marked on Monday, December 1, the fight against the syndrome remains stymied by the dearth of adequate treatment in poor countries and setbacks in finding an effective vaccine, experts say.

To be sure, there have been plenty of advances over the past two decades. While 33-million people have the human immunodeficiency virus (HIV) that causes AIDS, more are enjoying healthier, longer lives thanks to powerful new medications.

Organizers of World AIDS Day – built around the themes of leadership, self-responsibility and activism – are calling on governments to follow through on promises of universal treatment, prevention, care and support.

"We have effective treatments. We have no other choice than to offer them to all those who need them," said Jean-Francois Delfraissy, head of the French National Research Agency on AIDS and viral hepatitis (ANRS).

But affordable and effective treatment remains a rarity in Africa, home to the majority of HIV-positive people, making prospects of universal access to medication remote in the near future.

In poorer countries, the choice may eventually be between treating millions of HIV-positive patients, or offering more expensive treatment to about 500,000 people who are resistant to mainstream therapies, Delfraissy said.

Even in wealthier nations like France, where 5,200 new HIV-positive cases were registered last year, thousands of others remain unaware they are infected.

"Don't let AIDS pick up speed!" urges the French association AIDES, which plans to install a huge counter on the Paris opera house showing the lag between new infections and treatment.

On Friday, the United Nations urged countries to focus on the roots of the pandemic and draw on a panoply of tried-and-tested tools to help HIV from spreading among people most at risk.

"There is no single magic bullet for HIV prevention," said outgoing UNAids executive director Peter Piot.

Hopes for such a magic bullet were shattered last year, when scientists were forced to abandon two advanced clinical trials of an HIV/Aids vaccine by pharmaceutical company Merck, after they appeared to actually heighten the risk of infection.

But Aids research was given a boost in October when the 2008 Nobel Medicine Prize was bestowed to a pair of scientists who discovered HIV.

Researchers have also discovered new molecules and have launched tests on new triple treatments that have proved effective for patients no longer responding to other therapies

Meanwhile, research on finding an effective AIDS shot continues. US scientists recently discovered a gene that may pave the way for a vaccine.

Delfraissy, of ANRS, also predicts a revival in basic research to find molecules capable of attacking the virus at a stage where it has not yet been detected.

Scientists are also interested in the cases of some HIV-positive people who never develop full-blown AIDS.

"We have an impressive arsenal," said Father Pierre-Marie Girard, who heads the infectious disease unit for the Saint Antoine Hospital in Paris.

One mark of success, he said, is those with HIV today talk of living and aging well with the virus -- with hopes of enjoying the same lifespan as those without.

Christine Courcol contributes to the Mail & Guardian.