The spread of wild bird vectored avian influenza H5N1 in Europe enhanced during cold winters
11 august 2010 - Since the onset of highly pathogenic avian influenza H5N1 (H5N1 HPAI) epidemics in late 2003 a total of 62 countries or territories have reported cases of this disease in poultry and wild birds. Of these, 26 are located in Europe. Particularly in eastern Asia and Egypt does this zoonotic disease remains detrimental to animal and human health, with significant impacts on food security, economic progress, social stability and livelihoods.
A direct relationship between cold weather and the incidence of influenza has since long been established. In January 2006, a major cold spell affected Europe, coinciding with an increase of H5N1 HPAI detected in wild birds, mostly dead mute swans, starting along the River Danube and the Mediterranean coast line. In subsequent weeks H5N1 HPAI detections in wild birds were concentrated in central and western parts of Europe, reaching a peak in mid February 2006.
An FAO research team investigated whether the geographic distribution of these H5N1 HPAI infections was modulated by the long-term wintering line, that is, the zero degree Celsius isotherm marking the limit beyond which areas are largely unsuitable for wintering waterfowl. This analysis shows that H5N1 HPAI detection sites were closer to the wintering line than would be expected by chance.
The rationale is that partial frost conditions in water bodies in wild bird wintering areas throughout Europe are conducive to bird congregation, enhancing H5N1 HPAI transmission and local spread. H5N1 HPAI hotspots build up environmental virus loads so that the virus may locally persist until spring, at least in cooler areas proximate to the wintering line.
The practical implication of this finding is that anomalous cold weather periods would therefore represent a warning signal for authorities to step up wild bird influenza surveillance in European wintering sites. More about these findings and other details in relation to this topic can be found in 'The Cold European Winter of 2005ľ2006 Assisted the Spread and Persistence of H5N1 Influenza Virus in Wild Birds' published in EcoHealth journal, August 2001.
The Food and Agriculture Organization of the United Nations (FAO) undertakes this type of study in order to reveal feasible and viable options to address high-impact transboundary diseases that are emerging and re-emerging around the world.