Researchers from Columbia and Harvard Universities have discovered a link between the La Nina weather pattern and the flu pandemics of 1918, 1957, 1968 and 2009. This research was published in the PNAS (Proceedings of the National Academy of Sciences).
La Nina periodically brings cool water to the surface of the Pacific Ocean making for warmer, dryer winters and lasts about 5 months. As La Nina weather patterns arrive birds migrating patterns become altered thus promoting new strains of the flu to begin. The study authors noted research that showed the La Nina pattern alters the migration, stopover time, fitness and inter-species mixing of migratory birds. These conditions may favor the kind of gene swapping, or genetic re-assortment, that creates new and potentially more variations of the influenza virus.
The migration patterns may also affect how birds come in contact with domestic animals like pigs who are known to carry swine flu and are common throughout pig populations. Though rare, Swine flu transmission can occur over to humans as in the case with the Minnesota infant boy last month.
On average La Nina weather patterns occur every 3-5 years and can be back-to-back as in the case this season. We wonder though why did the flu pandemics occur only during certain La Lina patterns of 1918, 1957, 1968 and 2009? And can La Nina also lead to other infectious diseases to spread more easily? Drop us your thoughts in the comments.