Washington: The swine flu strain that has killed more than 1,200 people in India since December has acquired mutations that make it more dangerous than previously circulating strains of H1N1 influenza, a new MIT study suggests.

The study by two Indian-American researchers contradicts previous reports from Indian health officials that the strain has not changed from the version of H1N1 that emerged in 2009 and has been circulating around the world ever since.