La Niña weather patterns linked to flu pandemics

A new study co-authored by HSPH’s Marc Lipsitch links the four most recent influenza pandemics (1918, 1957, 1968, and 2009) to the weather pattern known as La Niña. During these periods, the surface temperature in the equatorial Pacific cools and can alter the migratory patterns of birds. This likely brings together birds that typically don’t mix and also changes their contact with domestic animals—conditions that favor the genetic mixing that occurs when an animal is infected with multiple forms of the influenza virus,  and can ultimately lead to the development of dangerous novel pandemic strains. Not all La Niña years see the development of a new influenza strain, however all four of the pandemics studied were preceded by these conditions.

Co-author Jeffrey Shaman of Columbia University told the Toronto Star that more research is necessary before weather patterns can be used to forecast pandemics.

“It’s a neat idea that comes from a limited amount of data,” he said. “It could be a coincidence. But if it’s causal, there is an opportunity to predict pandemics.”

The study appeared in the January 17 Proceedings of the National Academy of Sciences. Read abstract.

Read Toronto Star and UPI articles.

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Read articles about influenza research at HSPH (Harvard Public Health Review)