Flu in full flight: On the avian flu outbreak

The avian flu must be stopped before sustained transmission among humans

Just three months after India declared itself to be free of the avian influenza outbreak, the highly pathogenic avian influenza subtypes, H5N1 and H5N8, have been reported from a dozen epicentres in four States — Rajasthan, Madhya Pradesh, Himachal Pradesh and Kerala. In addition, thousands of poultry birds have died in Haryana, while Jharkhand and Gujarat, too, have sounded an alarm; the cause in these three States is still unknown. The two subtypes have targeted different birds — crows in Rajasthan and Madhya Pradesh, migratory birds in Himachal Pradesh, and poultry in Kerala. While tests have confirmed H5N1 for causing the deaths of over 2,000 migratory birds in Himachal Pradesh, H5N8 has been identified for killing thousands of poultry in Kerala, and hundreds of crows in Rajasthan and Madhya Pradesh. In a bid to stop the spread, as on Wednesday over 69,000 birds, including ducks and chickens, were culled in Alappuzha and Kottayam as per India’s 2015 National Avian Influenza Plan. Other States have been asked to be vigilant of any unusual deaths or disease outbreak signs amongst birds, particularly migratory ones. Migratory birds have been largely responsible for long-distance transmission of the virus into India during winter. It then spreads through local movement of residential birds and poultry. Movement of men and material from poultry farms too has been a cause for further spread. This is why States have been asked to strengthen biosecurity of poultry farms, disinfection and proper disposal of dead birds. With backyard rearing of poultry birds common, the task of elimination will be particularly difficult.

A recent European Food Safety Authority report says 561 avian influenza detections were made between August-December in 15 European countries and the U.K. The virus was predominantly found in wild birds, and a few in poultry and captive birds. H5N1 and H5N8 were two of three subtypes found in Europe. Genetic analysis helped confirm the spread from Asia to west-central Europe, suggesting a “persistent circulation of this virus strain, likely in wild birds in Asia”. While avian influenza virus crossing the species barrier and directly infecting humans happens occasionally, human-to-human spread has been rare. But mutations or genetic reassortment of an avian influenza A virus and a human influenza A virus in a person can create a new influenza A virus that could likely result in sustained transmission between humans, thus increasing the risk of a pandemic influenza. Hence, all efforts should be directed at stamping out the outbreaks in the affected States. It is also important to undertake genome sequencing of virus samples to track the evolution of the virus.

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