While the country had reported outbreaks of the highly pathogenic avian influenza (bird flu) from 2006-08 and experts had questioned the role of migratory birds in the transmission of the virus, a latest study by the National Institute of Virology (NIV) and city-based Ela Foundation said none of the birds had tested positive for H5N1.

India had reported outbreaks of the avian influenza H5N1 in poultry in the states of Maharashtra, Gujarat and Madhya Pradesh (February-April 2006); Manipur (July 2007); West Bengal (January 2008) and Tripura (April 2008). Since the role of migratory birds in the transmission of avian influenza was not clear, an Avian Influenza (AI) surveillance in wild migratory, wild resident, domestic birds and poultry was undertaken by the NIV and Ela Foundation in 2006-07.

The study did not report any H5N1 or any other AI viruses from sampled birds during the study period. Although AI virus has been reported earlier in the species/families of birds elsewhere, the screened population in the present study was free from any infection. No convincing evidence has yet shown that infected, asymptomatic wild birds can or do carry influenza virus along established, seasonal long-distance migration routes, said Dr Satish Pande, trustee of Ela foundation who, along with NIV and other ornithologists, has published the findings in the August issue of the journal Science.

Considering the lower rate of virus isolation, it is justified to screen larger sample sizes for AI surveillance, over a longer period of time and to cover more species. About 1,298 avian species have been recorded from the Indian subcontinent of which about 1,001 species are resident and 159 (12 per cent) species are winter migrants. We tested 36 wild bird species, which represent 31 per cent and 41.2 per cent of the species and families respectively, found AI positive globally, said Pande.

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