Wpływ warunków meteorologicznych na zachorowalność na grypę w wybranych polskich miastach = Impact of meteorological conditions on influenza morbidity in the selected Polish cities

Abstract

This study was designed to explore the impact of meteorological factors (air temperature, relative and absolute humidity, wind, cloudiness and precipitation) on influenza morbidity in four selected big cities in Poland – Cracow, Poznań, Warsaw and Wrocław. Atmospheric data obtained from four meteorological stations spread over six years (2013‑2018) were compared to influenza-like illnesses (ILI) reports, obtained from the Voivodship Units of the State Sanitary Inspection for the same locations and period. Data were analysed using Spearman correlation and negative binomial regressions to capture the nonlinear relationship between exposure to environmental conditions and influenza morbidity. Our study found a strong negative association of absolute air humidity with influenza infections (RR = 0.738) and positive relationship with minimal temperature (RR = 1.148). The effect of wind speed, cloudiness and precipitation on ILI was less evident. Proposed model is valid for all age groups in Polish cities, but suits the best to elderly citizens (65+). The model is also appropriate for different seasons, however only absolute humidity, minimal temperature and wind speed are considered significant variables all year round. Furthermore, we observed 6 to 9-days delay between particular adverse weather conditions and ILI morbidity increase, as 1-week lag model proved to have the highest predictive power (AIC = 8644.97). Although meteorological variables have statistically significant contribution to explain influenza morbidity, there are also other non-climatic factors, that can possibly influence the seasonality and complexity of influenza epidemiology in Polish cities.