Scientists link bird flu outbreaks with cold fronts in EU

Outbreaks of H5N1 flu among birds in Europe came at the edges of cold fronts that caused wild birds to change migration patterns, scientists said on Thursday (April 8), suggesting cold snaps may signal future outbreaks.

Dutch and American researchers found European outbreaks of bird flu during the 2005-06 winter were driven by collective movements of wild waterbirds to places where the fresh water they need to feed and survive had not frozen.

"This has important implications for surveillance, which should target areas where temperatures are close to freezing in winter, especially in poultry-dense regions close to areas where waterfowl aggregate," the researchers said.

The virus emerged more than a decade ago in poultry in Southeast Asia. In 2005 it spread outside Asia infecting both poultry and wild birds in the Middle East, Europe and Africa.

Last month, Romanian officials reported an outbreak of bird flu on a poultry farm close to Ukraine in an area on an important migratory pathway for wild birds.

Leslie Reperant of Princeton University in the US and Thijs Kuiken of the Erasmus Medical Center in the Netherlands said their findings offered a possible way to predict and control where and when bird flu might erupt again.

They found that most H5N1 outbreaks occurred at sites where maximum temperatures were between 0 degrees Celsius and 2 degrees Celsius. This was usually on the edge of cold fronts where fresh water remained unfrozen.

"To minimise the distance flown, they also try to stay as close as possible to the northern breeding grounds to which they will migrate during spring. The resulting congregation of different species of waterbirds along the freezing front likely created ideal conditions for the transmission of the H5N1 virus," researchers concluded.