In trying to understand the route that the Avian influenza virus H5N1 has taken to get into India, scientists have found that the virus isolated from a focal outbreak in 2007 was different from any other reported from neighbouring countries in the subcontinent. The finding suggests that the virus may have been introduced here from an independent source1.
Researchers from the National Institute of Virology genetically characterised the virus isolates from a focal H5N1 outbreak in poultry from Manipur, a north-eastern state, of India, in 2007. They tried to understand its relationship with other H5N1 isolates and to trace the possible source of introduction of the virus into the country.
Characterization of the complete genome revealed that the virus belonged to clade 2.2. It was distinctly different from viruses of the three EMA sublineages of clade 2.2 but related to isolates from wild migratory waterfowl from Russia, China and Mongolia.
The team concluded that the acquisition of polymorphisms as seen in recent isolates of 2005-07 from distinct geographical regions suggested the possibility of transportation of H5N1 viruses through migratory birds.
"Considering that all eight genes of the earlier Indian isolates belonged to the EMA3 sublineage and similar strains have not been reported from neighbouring countries of the subcontinent, it appears that the virus may have been introduced independently," the team said.
