Like that one kid who gets everyone in the classroom sick, nature's problem child, La Niña, may be responsible for deadly flu pandemics.
La Niña conditions in the equatorial Pacific preceded the four most recent influenza pandemics in 1918, 1957, 1968 and 2009, said Jeffrey Shaman of Columbia University and Marc Lipsitch of the Harvard School of Public Health in the Proceedings of the National Academy of Sciences.
BLOG: La Niña: Baby's Back but the Child is Mild
The cooler ocean temperatures associated with La Niña reroute bird migrations and change birds' fitness, stopover times and contacts with different bird species, noted the authors.
"We know that pandemics arise from dramatic changes in the influenza genome. Our hypothesis is that La Niña sets the stage for these changes by reshuffling the mixing patterns of migratory birds, which are a major reservoir for influenza," said Shaman in a press release.
The changes may also increase the birds contact with domestic pigs, leading to even more disease risk.. Gene-swapping between avian and pig influenza occurred in the 2009 swine flu epidemic.
IMAGE: Avian influenza warning sign in the UK (Keith Evans, Wikimedia Commons)
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