Quantifying the role of weather on seasonal influenza

Abstract

BackgroundImproving knowledge about influenza transmission is crucial to upgrade surveillance network and to develop accurate predicting models to enhance public health intervention strategies. Epidemics usually occur in winter in temperate countries and during the rainy season for tropical countries, suggesting a climate impact on influenza spread. Despite a lot of studies, the role of weather on influenza spread is not yet fully understood. In the present study, we investigated this issue at two different levels.MethodsFirst, we evaluated how weekly (intra-annual) incidence variations of clinical diseases could be linked to those of climatic factors. We considered that only a fraction of the human population is susceptible at the beginning of a year due to immunity acquired from previous years. Second, we focused on epidemic sizes (cumulated number of clinical reported cases) and looked at how their inter-annual and regional variations could be related to differences in the winter climatic conditions of the epidemic years over the regions. We quantified the impact of fifteen climatic variables in France using the Réseau des GROG surveillance network incidence data over eleven regions and nine years.ResultsAt the epidemic scale, no impact of climatic factors was highlighted. At the intra-annual scale, six climatic variables had a significant impact: average temperature (5.54 ± 1.09 %), absolute humidity (5.94 ± 1.08 %), daily variation of absolute humidity (3.02 ± 1.17 %), sunshine duration (3.46 ± 1.06 %), relative humidity (4.92 ± 1.20 %) and daily variation of relative humidity (4.46 ± 1.24 %). Since in practice the impact of two highly correlated variables is very hard to disentangle, we performed a principal component analysis that revealed two groups of three highly correlated climatic variables: one including the first three highlighted climatic variables on the one hand, the other including the last three ones on the other hand.ConclusionsThese results suggest that, among the six factors that appeared to be significant, only two (one per group) could in fact have a real effect on influenza spread, although it is not possible to determine which one based on a purely statistical argument. Our results support the idea of an important role of climate on the spread of influenza.Electronic supplementary materialThe online version of this article (doi:10.1186/s12889-016-3114-x) contains supplementary material, which is available to authorized users.

On the global trends and spread of the COVID-19 outbreak: preliminary assessment of the potential relation between location-specific temperature and UV index

“…With very small σ value of the distribution, it is very apparent that the temperature band for community infection is, indeed, very narrow. Previous studies have clearly demonstrated that lower temperatures are directly related to influenza virus activity (Deyle et al 2016;Ianevski et al 2019;Roussel et al 2016). Thus, it is clear that increasing temperature may have some clear indication for the reduction in the number of infected cases.…”

Climatic Factors and Influenza Transmission, Spain, 2010–2015

“…Influenza epidemics in temperate regions show a characteristic seasonal pattern with peak incidence occurring in winter [ 1 ]. Different studies in different countries show that in those periods when absolute humidity and the temperatures in a region are lower, the risk of influenza transmission increases [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ].…”

A longitudinal ecological study of seasonal influenza deaths in relation to climate conditions in the United States from 1999 through 2011

“…They observed in temperate climates that there were peaks in seasonal influenza epidemics during the months of lowest temperature, humidity, and solar radiation [11]. Similarly, other investigators examined in the temperate climate of France the relationship between the annual incidence rate of seasonal influenza and climate conditions in different regions in France [12]. They reported that the climate conditions associated with variations in temperature, humidity, and sunshine were significantly related to the weekly incidence rate of influenza within a single year.…”