Global environmental drivers of influenza
Deyle, E. R., Maher, M. C., Hernandez, R. D., Basu, S., & Sugihara, G. (2016). Global environmental drivers of influenza. Proceedings of the National Academy of Sciences, 113(46), 13081-13086. doi:10.1073/pnas.1607747113
Summary
- Bottom line: A 2016 study using an approach known as empirical dynamic modeling (EDM) has found that a key environmental driver – absolute humidity – links influenza outbreaks across the globe. The research was, in part, an unexpected result of a grant from the Lenfest Ocean Program to study a small, oily fish called Gulf menhaden using that same approach.
- Background: Flu outbreaks are strongly seasonal in temperate regions. In the tropics, flu is also widespread, but no direct link to seasonal temperature changes has been established.
- Methods: Using EDM, the study analyzed nearly 20 years of global influenza data to look for causal associations with four environmental factors: absolute humidity, temperature, relative humanity, and precipitation.
- Findings:
- The study uncovered an association between flu outbreaks, absolute humidity, and temperature across all latitudes. (Absolute humidity is the amount of moisture in the air, whereas relative humidity is the amount of moisture relative to what’s needed to saturate the air at the current temperature.)
- It found a critical temperature window of 70 to 75 degrees Fahrenheit (21-24 degrees Celsius). At temperatures below this window, higher humidity reduces incidence of influenza, but at warmer temperatures it increases incidence. This information may be helpful in guiding indoor climate control and in predicting tropical flu outbreaks.
The full publication is available here:
