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 strain and 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 of genogroups in India and more new strains are likely to emerge, making common vaccine a difficult task.
Mixed genogroups of  swine flu virus (S-OIV) have been circulating in the country after the main virus derived from the Californian strain has evolved here. "There should be a continuous monitoring of the genetic makeup of this newly emergent virus for a better understanding of its  evolution," said Dr P Manmohan, whose team conducted a study of the human influenza virus.
Studies on the strain caused by the swine flu virus in Gwalior two years ago revealed 99 per cent homology with California and other circulating novel swine flu viruses. However, the researchers found three major changes at nucleotide level. They also noticed two major amino acid shifts in relation to the prototype strain. The HA gene sequence phylogeny revealed the circulation of two genetically distinct lineage belonging to Clade VII and Clade I of S-OIV.
Since swine flu was first detected in India in May 2009, the virus has claimed 621 people and 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 and new strains are likely to emerge in future.
Of these strains, the first one to be isolated in India was from Hyderabad. It is named A/India-Hyd/NIV51/2009). A traveller from the USA was infected by this strain when he landed in the city on May 13, 2009.
The sequence analysis of these Indian isolates revealed specific mutation at nucleotide level and amino acid changes respectively with respect to 22 global H1N1 pandemic isolates including a few Indian isolates. Diversity of these Indian isolates revealed the co-circulation of Clade VII and Clade I with predominance of Clade VII as already reported from Southern India.
Multiple lineages of influenza A viruses were found to co-circulate during any single season and to undergo frequent reassortment. This, in turn, has had a major impact on antigenic evolution.