Indians infected with the Aids virus are more likely to contract the disease than people in the west, a new study has found.
India is home to one in seven HIV-positive people
Scientists say that Indians have lower immunity to the virus because they have genes that hasten the disease.
India says more than five million of its citizens are infected with the HIV virus, second only to South Africa.
Activists say the number of Indians affected by HIV/Aids is much higher than the government says.
Scientists at India's premier medical school, the All India Institute of Medical Sciences (AIIMS), studied 200 people with HIV infection and 2000 healthy people over two years for the study.
They found that the HLA-B*35-Px gene linked to rapid progression from HIV infection to Aids is "two-and-a-half times" more common in Indians than a protective gene called HLA-B*35-Py.
They also found that that a "protective variant" of chemokines - intracellular messenger molecules whose major function is to attract immune cells to sites of infection - was not present among Indians.
"Protective genes are low among Indians while the harmful genes are more common," Dr NK Mehra, head of the study told the BBC.
A leading Indian HIV/Aids expert Dr Smarajit Jana says that this could be a major finding.
India has been trying to develop an AIDS vaccine
"If true, it could open up more research on genetic factors and regarding the path from HIV infection to Aids," he said.
Last July, India's National Aids Control Organisation (Naco) said that the country had 5.1 million infections, second only to South Africa which has 5.3 million people living with HIV or Aids.
Two years ago, the United States National Intelligence Council estimated there were five million to eight million HIV-infected people in India, a number it said could swell to 20-25 million by 2010.
The Indian government says there is no need to panic as only 0.5% of Indians have been infected, compared to 2.1% in Thailand and 2.3% in South Africa.
Half of India's new HIV infections occur in the 10-25 age group but only 59% of adolescents in the country are familiar with condoms, according to a government report.
The report says the level of HIV infection among women is likely to go up, with increasing numbers of married women being infected by their husbands.