Effects of circulation weather types on influenza hospital admissions in Spain

In this study, we use a statistical approach based on generalized additive models, linking atmospheric circulation and the number of influenza-related hospital admissions in the Spanish Iberian Peninsula during 2003-2013. The relative risks are estimated for administrative units in the Spanish territory, which is politically structured into 15 regions called autonomous communities. A catalog of atmospheric circulation types is defined for this purpose. The relationship between the exposure and response variables is modeled using a distributed lag nonlinear model (DLNM). Types from southwest and anticyclonic are significant in terms of the probability of having more influenza-related hospital admissions for all of Spain. The heterogeneity of the results is very high. The relative risk is also estimated for each autonomous community and weather type, with the maximum number of influenza-related hospital admissions associated with circulation types from the southwest and the south. We identify six specific situations where relative risk is considered extreme and twelve with a high risk of increasing influenza-related hospital admissions. The rest of the situations present a moderate risk. Atmospheric local conditions become a key factor for understanding influenza spread in each spatial unit of the Peninsula. Further research is needed to understand how different weather variables (temperature, humidity, and sun radiation) interact and promote the spread of influenza.

Automated summary

Using a statistical approach based on generalized additive models, this study examined the relationship between atmospheric circulation and the number of influenza-related hospital admissions in the Spanish Iberian Peninsula from 2003 to 2013. Results show that southwest and anticyclonic atmospheric circulation types have a significant impact on increasing the probability of influenza-related hospital admissions. The study also identified specific situations of extreme and high risk of influenza-related hospital admissions under different weather conditions.