Washington: The swine flu virus in India, which has already killed more than 1,500 people since December may have acquired mutations that make it more severe and infectious than previously circulating H1N1 strains, a new MIT study has warned.

The study by Massachusetts Institute of Technology (MIT) contradicts previous reports from Indian health officials that the strain has not changed from the version of H1N1 that emerged in 2009.

MIT researchers found that the recent Indian strains carry new mutations in the hemagglutinin protein that are known to make the virus more virulent.

Hemagglutinin binds to glycan receptors found on the surface of respiratory cells and the strength of that binding determines how effectively the virus can infect those cells.

In the past two years, genetic sequence information of the flu-virus protein hemagglutinin from only two influenza strains from India has been deposited into publicly available influenza databases which makes it difficult to determine exactly which strain is causing the new outbreak and how it differs from previous strains.

"However, those two strains yielded enough information to warrant concern," said Ram Sasisekharan, the Alfred H Caspary, professor of Biological Engineering at MIT and the paper's senior author.

Sasisekharan and Kannan Tharakaraman, a research scientist in MIT's Department of Biological Engineering, compared the genetic sequences of those two strains (of 2014) to the strain of H1N1 that emerged in 2009 and killed more than 18,000 people worldwide between 2009 and 2012.

One of the new mutations is in an amino acid position called D225, which has been linked with increased disease severity, researchers said.

Another mutation, in the T200A position allows hemagglutinin to bind more strongly to glycan receptors, making the virus more infectious, the study found.

Sasisekharan said that more surveillance is needed to determine whether these mutations are present in the strain that is causing the current outbreak, which is most prevalent in Gujarat and Rajasthan and has infected more than 20,000 people so far.

Meanwhile, in New Delhi health ministry officials said they will take up the issue with the Indian Council of Medical Research (ICMR) since the latter has been saying till now that there have not been any mutations.

"So far the ICMR has been saying that there is no mutation. But since the study has come up, we will take it up with ICMR for a final view," additional secretary, health, Arun Panda said.

According to the latest figures from the Union health ministry data, as of March 10, as many as 1,537 people have perished due to swine flu while the number of infected people in the country is 27,234.