India has less than half the number of HIV/AIDS cases than was previously thought, and fewer than both South Africa and Nigeria, according to a comprehensive new study that was unveiled today.

UNAIDS, the United Nations agency, estimated last year that India had the highest HIV caseload in the world, with 5.7 million people infected. The Indian government put the figure at 5.2 million.

But a more authoratitive survey completed this year involving UNAIDS, the Indian government and several international organisations found that India had about 2.47 million cases.

South Africa has an estimated 5.5 million and Nigeria three million.

“Today we have a far more reliable estimate of the burden of HIV in India,” Anbumani Ramadoss, the Health Minister, told a news conference.

“We have about 2.47 million estimated cases, which is huge in terms of numbers,” he said. “In terms of human lives affected, the number is still large, in fact very large. This is very worrying for us.”

India’s HIV infection rate is now estimated at around 0.36 percent of the population of more than 1.1 billion, compared with a previous estimate of 0.9 percent, he said.

Infection rates in South Africa, Nigeria and many other African countries are far higher because of the relatively small size of their populations. In Botswana, more than a third of the population are thought to be HIV positive.

The survey results appear to indicate that India is not as close to an African-style AIDS epidemic as many experts had previously feared.

They are particularly welcome for the Indian government, which has long accused Western AIDS specialists of exaggerating the scale of the problem in India.

But they have raised fears that Indian politicians could grow complacent and cut funding for the fight against AIDS in a country where an estimated 40 percent of women have not even heard of the disease.

The results were released as the government launched a new $2.8 billion National AIDS Control Programme, which aims to expand prevention campaigns and free treatment for HIV-positive people.

Some Indian officials have hailed the apparent decline in HIV infections as proof that their prevention campaigns are working.

But most AIDS experts say the lower figures simply reflect the more reliable data gathered in the latest survey.

“It’s not a surprise that the figures are lower,” Dennis Broun, the India country director for UNAIDS, told The Times.

“To reach our previous estimate, we had to make a whole lot of assumptions and use a small number of samples to reach a figure for over a billion people.”

UNAIDS calculated its previous estimate by using hundreds of surveillance centres to test the blood of pregnant women and high-risk groups such as sex workers, intravenous drug users and men who have sex with men.

The new estimate is based in large part on the results of a state National Family Health Survey which took blood samples from 102,000 members of the general public -– rather than specific high risk groups.

It also included information from a behavioural and testing study of 25,000 people from high-risk groups, funded by Avahan, the AIDS arm of the Bill and Melinda Gates Foundation.

And it placed greater emphasis on northern India than previous studies, which skewed national estimates towards southern states with higher infection rates.

The southern state of Andhra Pradesh, for example, has almost 20 percent of India’s AIDS cases with less than five percent of its population.

Dr Broun said UNAIDS and other organizations should not ease up their prevention programmes as India’s caseload was still high and AIDS awareness negligible in much of the country.

But he admitted that India’s epidemic was largely confined to high risk groups, and had not yet spread to the general population.

The new survey, he said, showed that India still had a chance to curb infection rates and achieve universal access to treatment for HIV positive people.

“It looked like a daunting task before, but now I think it’s reachable,” he said.

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