India's National Institute of Virology has disputed the findings of researchers from the Massachusetts Institute of Technology that the deadly swine flu virus has undergone mutations.
The MIT study said that the genetic information of two Indian strains, deposited in public databases in the past two years, revealed new mutations to a virus strain that originated in California in 2009.
The Indian strain is far more virulent, they said, and could evade the vaccine developed for the California strain. The Californian strain contributed to the pandemic, which caused over 284,000 deaths across 74 countries worldwide during 2009-10.
Rejecting the findings as "incorrect", the NIV said: "We found that the strain analysed in the said publication and the sequence data of the original H1N1 virus ... did not show any of these mutations."
The strain analysed in the US study had no relevance to the current outbreak, it said.
The MIT researchers called for greater surveillance to determine whether the mutations were currently present in India.
"... effectiveness of the current H1N1 flu vaccine is debatable, and there have been calls for updating the vaccine. The Indian H1N1 viruses that circulated in 2014 are different compared to the 2009 vaccine strain A/California/07/2009," said Ram Sasisekharan from the MIT.
Other experts too have called for increased surveillance of the influenza in India while cautioning against any conclusions based on the sequence analysis of two strains.
Toll nears 2000
The death toll from swine flu in India rose to 1,674 while the number of persons affected by the H1N1 virus exceeded 29,000 as on 13 March, according to the health ministry.
Experts have been suggesting that a new strain of influenza virus responsible for 99.8% flu infections in the US this season could be behind the swine flu outbreak in India.
The H3N2 virus is one of the three sub-types of swine flu but labs in India are only looking for H1N1 strains. H2N2 is the other strain.
The World Health Organization raised an alarm over the widespread and severe influenza in many parts of the world mainly arising from an antigenic drift or mismatch between the strain used in the vaccine and that found in the community.
WHO is particularly concerned about avian influenza with the highly pathogenic H5N1 avian influenza virus joined by five new strains in five years.