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By Kamil Zaheer

NEW DELHI, July 6 (Reuters) - The number of people living with HIV/AIDS in India is 2.47 million, less than half of previous official estimates, according to new U.N.-backed government estimates released on Friday.

India was thought to have the world's biggest HIV-positive caseload with 5.7 million infections but the new estimate puts it below South Africa and Nigeria.

The new figure was calculated with the help of the United Nations and United States Agency for International Development.

"We have about 2.47 million estimated cases which is huge in terms of numbers," Health Minister Anbumani Ramadoss told a news conference. "In terms of human lives affected, the number is still large, in fact very large. This is very worrying for us."

The prevalence level of the infection was now estimated to be around 0.36 percent of the more than 1.1 billion population from the earlier 0.9 percent, he said.

The minister's comments came at the launch of the country's new $2.8-billion National AIDS Control Programme, which aims to expand free treatment for HIV-positive people and roll back the epidemic through more prevention campaigns.

Previously, the United Nations had arrived at the 5.7 million figure by using hundreds of surveillance centres to test the blood of pregnant women and high-risk groups such as injecting drug users and prostitutes over four months each year.

But a new population-based survey that took the blood samples of 102,000 people to test for HIV among the general public -- rather than specific groups -- indicated for the first time India's HIV caseload was highly overestimated.

The UNAIDS agency says population surveys that do not depend on someone going to a specific government clinic are "more representative" and generate "more accurate information" for rural areas and the male population.

"MORE PRECISE" ASSESSMENT

To determine the new estimate, both the population survey and surveillance data were used.

"The prevalence from the national survey has been used as almost a starting base," Peter Ghys, UNAIDS's Geneva-based Manager of Epidemic and Impact Monitoring, told Reuters.

"The expanded sources of data give us a much more precise assessment of what the status is of the epidemic," he added. "The new estimate is closer to the true prevalence."

Health experts say that in a number of countries, HIV caseloads and prevalence rates have fallen, often sharply, after they carried out population-based surveys.

In India, the fact that government surveillance centres are mainly visited by poorer people -- who are more affected by HIV -- and high risk groups led to the national estimate to be skewed upwards, they add.

Ramadoss said there was no plan to reduce funding for AIDS because of the lower estimate and added the government may actually increase funding, as 140 of India's 604 districts had a HIV prevalence of more than 1 percent.

Sujatha Rao, the head of the state-run National AIDS Control Organisation, said India could not let down its guard.

"This is our last window of opportunity to reverse the epidemic and ensure it does not get into the general population because if it does, we are done for," Rao said.

Voluntary groups running anti-HIV/AIDS campaigns say the new, lower numbers should not deflect attention from the need to curb the spread of the deadly virus in a country with a crumbling government healthcare system.

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