It has long been thought that there are linkages between certain viruses and the weather. The flu season is winter (in whichever hemisphere it happens to be winter in) for reasons having to do with the seasons. One early theory posited that the practices of East Asian farmers, as they tended their animals, caused waterfowl and swine and humans to share space closely enough that nasty new influenzas would emerge and spread around the world. Although that explanation for the annual seasonal flu has been dropped (if it ever really had wings… or hooves, or whatever) it is still possible that such a pattern could occur. One of the more likely places to look for this sort of thing is with bird flu, because there are large numbers of migratory birds that host the flu, and the interaction of wild and domestic birds is not an incredibly unlikely event.
A paper just out in PLoS Pathogens explores a link between a virus, seasonal change, and wild birds.
The very nasty avian influenza H5N1 virus has been hammering domestic fowl for over ten years now. There was a fairly widespread outbreak that reached beyond its original distribution in Asia in 2005, affecting domestic poultry and wild birds. It was understood that the movement of domestic birds was part of this process, but the question remained open as to how much the spread of this H5N1 virus was due to the movement of wild birds.
…. the ability of wild birds to carry the virus to novel geographical areas is still highly debated and remains obscure. In Europe, the virus mainly infected wild birds, and emergence coincided with a spell of cold weather, which is known to result in massive movements of wild waterbirds. … we demonstrate that movements of wild waterbirds associated with cold weather contributed to the spread and geographical distribution of outbreaks in Europe during the winter of 2005-2006. Higher density of wild waterbirds on bodies of water that remain unfrozen ahead of the freezing line likely favoured transmission of the virus and resulted in distinctive distribution of outbreaks at locations where surface air temperatures were 0°C-2°C. 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.
This also signifies a likely effect on the spread of bird flue from global warming.
As part of this study, the researchers made an interesting graphic: It is a video that you can download and play which shows the relaionship between air temperature near the ground and avian flu spread. Click here to download the file.
Leslie A. Reperant, Neven S. Fučkar, Albert D. M. E. Osterhaus Andrew P. Dobson, & Thijs Kuiken (2010). Spatial and Temporal Association of Outbreaks of H5N1 Influenza Virus Infection in Wild Birds with the 0°C Isotherm PLoS Pathology, 6 (4) DOI: 10.1371/journal.ppat.1000854.t001