LONDON - The number of AIDS cases worldwide fell from almost 40 million cases last year to about 33.2 million cases in 2007, global health officials reported Tuesday.
It sounds like dramatic progress in slowing the virus's spread but the decline is mostly just on paper.
Previous estimates were largely inflated and the new numbers are the result of a new methodology, which shows the AIDS pandemic is losing momentum.
"For the first time, we are seeing a decline in global AIDS deaths," said Dr. Kevin De Cock, director of the World Health Organization's AIDS department.
On Wednesday, WHO and the United Nations AIDS agency will issue their annual AIDS report, after convening an expert meeting last week in Geneva to examine their data-collection methods.
Much of the global drop in AIDS cases is due to revised numbers from India - which earlier this year slashed its numbers in half, from about six million cases to about three million - and to new data from several countries in sub-Saharan Africa.
UN officials could not rule out future downward corrections. In their assessment of the global AIDS epidemic, WHO and UNAIDS experts reported there were 2.5 million people newly infected with HIV in 2007. Just a few years ago, that figure was about five million.
Previous AIDS numbers were largely based on the numbers of infected pregnant women at antenatal clinics, as well as projecting the AIDS rates of certain high-risk groups like drug users to the entire population at risk. Officials said those numbers were flawed and they are now incorporating more data like national household surveys.
Yet while the global AIDS numbers are falling, there are huge regional differences. Sub-Sarahan Africa remains the epicentre of the epidemic. AIDS is still the leading cause of death there, where it affects men, women and children. Elsewhere in the world, AIDS outbreaks are mostly concentrated in homosexual men, intravenous drug users and sex workers.
But the UN said progress is being made and the global epidemic peaked in the late 1990s.
"There are some encouraging elements in the data," said De Cock.
He said the dropping numbers are proof some of the UN's strategies to fight AIDS are working.
Not everyone agrees. Some critics have accused the UN of inflating its AIDS numbers and say the revised figures are long overdue.
"They've finally got caught with their pants down," said Dr. Jim Chin, a clinical professor of epidemiology at the University of California at Berkeley.
Chin is a former WHO staffer and the author of "The AIDS Pandemic: The Collision of Epidemiology with Political Correctness."
Chin said it is difficult to tell whether the lowered numbers are evidence AIDS treatment and prevention strategies are working, or whether the decrease is just due to a natural correction of previous overestimates.
Even with the revised figures, "the numbers are probably still on the high side," said Daniel Halperin, an AIDS epidemiologist at the Harvard School of Public Health.
Halperin attended the WHO/UNAIDS meeting last week that reviewed the figures and said the estimates are growing closer.
But because big numbers in public health translate into more money, there may be a reluctance among AIDS officials to admit fewer people are infected than they once thought, since that would cut their funding.
With limited money for public health, having good information is the key if countries are to spend money on health issues that most need it.
"On the one hand, it would be a mistake to radically decrease funding for HIV," Halperin said.
"But on the other hand, why not put more money into family planning or climate change?"
Other experts said even with the decreased figures, much more is needed to stop the AIDS pandemic.
"We are still failing to respond to the crisis," said Dr. Paul Zeitz, executive director of the Global AIDS Alliance.
"The overall prevalence of AIDS may have stabilized but we are still seeing millions of new infections and it is not time yet to step back from this battle."
