Title: Influenza epidemics are associated with temperature variability in Central Europe
Authors: Jan Kysely - Institute of Atmospheric Physics AS CR (Czech Republic) [presenting]
Hana Hanzlikova - Institute of Atmospheric Physics AS CR (Czech Republic)
Ales Urban - Institute of Atmospheric Physics AS CR (Czech Republic)
Jan Kyncl - National Institute of Public Health (Czech Republic)
Abstract: Influenza and acute respiratory infections (ARI) show seasonal patterns with winter incidence peaks and significantly contribute to excess winter mortality. A recent research suggests that influenza virus survival, transmission and seasonality can be modulated by weather conditions, such as periods of cold and dry air. We examined the relationships between environmental factors, epidemics of influenza/ARI and all-cause mortality in the population of the Czech Republic over 1982-2015. Epidemics were defined from weekly data on influenza/ARI morbidity, and differences between prevailing virus types were considered. The all-cause mortality data were controlled for long-term trends, seasonality, and the weekly cycle. The results showed that the seasonal onset of influenza/ARI epidemics was associated with temperature variability. The epidemics were typically preceded by 3-week periods of temperature fluctuations and prevailing westerly flow, suggesting frequent passages of air masses with humid air over Central Europe. The onset of severe epidemics with dominant H3N2 virus type was accompanied by pronounced changes in meteorological conditions, namely reduced westerly flow, intense cooling and low temperatures persisting several weeks. The relatively mild ambient temperatures before epidemics favour virus transmission and spreading in population while low temperatures during epidemics may enhance virus infectivity and prolong its survival.