What do changes in weather and stressed-out birds have to do with your health? In a study in Proceedings of the National Academy of Sciences, Jeffry Shaman of Columbia University and Marc Lipsitch of Harvard University are beginning to see a new link between La Nina conditions and outbreaks of the flu that could help governments and public health officials determine when the next pandemic will strike. To examine the connection between La Niña and flu pandemics, Shaman and Lipsitch looked at the four most recent, well-dated human influenza pandemics - 1918, 1957, 1968 and 2009 - and compared them to El Niño Southern Oscillation conditions. Is the relationship between the two causal or coincidental? What other factors could contribute to this strange concurrence? Find out more online.