India has fewer cases of HIV-Aids than previously thought and has almost certainly dropped behind South Africa as the country with the highest caseload.

UNAids, the United Nations agency, estimated last year that India had 5.7 million HIV cases compared with about 5.5 million in South Africa.

The Indian National Aids Control Organisation (Naco) put the figure at 5.2 million and some Indian officials accused Western Aids experts of exaggeration. Now a new study conducted by UNAids, Naco and other organisations is expected to end the debate by revealing a new total — possibly as low as 3.4 million — which they all agree will be the most accurate estimate to date. “There is so much more data. We’re going to arrive at a much more accurate picture,” Denis Broun, India country director for UNAids, told The Times.“What seems to be clear is that we’re going to have a prevalence lower than what we previously found.”

Although the 5.7 million figure was the highest numerically, because the South African population is 43 million against the 1.13 billion in India, the incidence of cases in the former is much greater.

It was too early to give a new figure, Dr Broun said, since the data was still being compiled and analysed and the Indian Government would not release the final report until the beginning of next month.

He added, however, that when UNAids made its estimate last year, the agency said that the real figure could be anywhere between 3.4 million and nine million. “Now we’re looking at a little lower than 3.4 million at the lower end and less than eight million at the higher end,” he said. “For the country as a whole, the risk of an Africa-type epidemic is very remote.” The Hindustan Times daily newspaper said at the weekend that the new estimate would be about 3.5 million.

The results represent a symbolic victory for the Indian Government, which has long argued that Aids experts overplay the number of cases.

It is investing £1 billion in schemes such as setting up free test centres and distributing free condoms and has raised this year’s budget for Aids prevention to 9.7 billion rupees (£120 million).

Officials attributed the study’s results in large part to prevention programmes among pregnant women and sex workers, especially in high-risk southern states such as Tamil Nadu and Karnataka.

Dr Broun and other Aids experts said that infection rates were rising among intravenous drug users and men who have sex with men. They said that the results were more a reflection of the improved methodology that they were using, rather than a change in the situation on the ground.

India previously measured HIV cases purely through state-run surveillance sites where blood samples are taken from pregnant women, men having sex with men, prostitutes and intravenous drug users. The new study, which was partly funded by USAid, the American overseas aid agency, expanded the number of surveillance sites to 1,100 from 700 in previous years.

More significantly, it included the findings of a government population health survey that tested 100,000 adults randomly between December 2005 and August 2006.

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