Flu Epidemics Linked to Weather Pattern
Researchers from Columbia University’s Department of Environmental Health Sciences have determined that the last four influenza pandemics – of 1918, 1957, 1968, and 2009 – were related to a Pacific Ocean weather pattern called La Niña.
All of these influenza outbreaks were preceded by the La Niña weather pattern, characterized by cooler than normal ocean surface temperatures along the central Pacific Ocean.
This condition, translated from Spanish to mean “the girl,” can last about five months, and often begins in the spring or summer months.
The La Nina pattern differs from the typical pattern of the El Niño Southern Oscillation – the predominant pattern. This La Nina cooling of ocean temperatures facilitates stronger storms, and a variety of atmospheric changes. La Nina often occurs every three or four years, but this is not consistent.
The La Nina pattern changes the migration patterns of migratory birds, along with that of their offspring. This, the researchers suggest, brings certain birds together with domestic animals – where the influenza virus can mutate.
The essential step is the mutation of bird flu viruses into a virus contagious to humans. This mutation step is known to occur through domestic animals – typically animals raised for slaughter such as pigs or chickens. The incubation of the virus within these domestic animals allows the virus to become transmittable to humans.
The researchers confirmed this as they stated:
“Changes in the phase of the El Niño-Southern Oscillation have been shown to alter the migration, stopover time, fitness, and interspecies mixing of migratory birds, and consequently, likely affect their mixing with domestic animals.”
La Nina conditions have been forecast to possibly increase during July and August of 2012.
Shaman J, Lipsitch M. The El Nino-Southern Oscillation (ENSO)-pandemic Influenza connection: Coincident or causal? Proc Natl Acad Sci U S A. 2012 Jan 17.