Novel human influenza virus H1N1 evolving into a new strain
By Syed Akbar Hyderabad: The novel human influenza virus H1N1 is evolving into a new strainand doctors fear that with the onset of monsoon, it will raise its ugly head once again.The novel human influenza or swine flu virus has already evolved into a number ofgenogroups in India and more new strains are likely to emerge, making common vaccine adifficult task. Mixed genogroups of swine flu virus (S-OIV) have been circulating in the country afterthe main virus derived from the Californian strain has evolved here. "There should be acontinuous monitoring of the genetic makeup of this newly emergent virus for a betterunderstanding of its evolution," said Dr P Manmohan, whose team conducted a study of thehuman influenza virus. Studies on the strain caused by the swine flu virus in Gwalior two years ago revealed 99per cent homology with California and other circulating novel swine flu viruses. However,the researchers found three major changes at nucleotide level. They also noticed twomajor amino acid shifts in relation to the prototype strain. The HA gene sequencephylogeny revealed the circulation of two genetically distinct lineage belonging to CladeVII and Clade I of S-OIV. Since swine flu was first detected in India in May 2009, the virus has claimed 621 peopleand affected 19,632 people across the country, mostly during monsoon and winter seasons.As many as seven lineages of the swine flu virus are in circulation in the country andnew strains are likely to emerge in future. Of these strains, the first one to be isolated in India was from Hyderabad. It is namedA/India-Hyd/NIV51/2009). A traveller from the USA was infected by this strain when helanded in the city on May 13, 2009. The sequence analysis of these Indian isolates revealed specific mutation at nucleotidelevel and amino acid changes respectively with respect to 22 global H1N1 pandemicisolates including a few Indian isolates. Diversity of these Indian isolates revealed theco-circulation of Clade VII and Clade I with predominance of Clade VII as already reported from SouthernIndia. Multiple lineages of influenza A viruses were found to co-circulate during any singleseason and to undergo frequent reassortment. This, in turn, has had a major impact onantigenic evolution.