Predicting Fluctuating Rates of Hospitalizations in Relation to Influenza Epidemics and Meteorological Factors.
BACKGROUND
In France, rates of hospital admissions increase at the peaks of influenza epidemics. Predicting influenza-associated hospitalizations could help to anticipate increased hospital activity. The purpose of this study is to identify predictors of influenza epidemics through the analysis of meteorological data, and medical data provided by general practitioners.


METHODS
Historical data were collected from Meteo France, the Sentinelles network and hospitals' information systems for a period of 8 years (2007-2015). First, connections between meteorological and medical data were estimated with the Pearson correlation coefficient, Principal component analysis and classification methods (Ward and k-means). Epidemic states of tested weeks were then predicted for each week during a one-year period using linear discriminant analysis. Finally, transition probabilities between epidemic states were calculated with the Markov Chain method.


RESULTS
High correlations were found between influenza-associated hospitalizations and the variables: Sentinelles and emergency department admissions, and anti-correlations were found between hospitalizations and each of meteorological factors applying a time lag of: -13, -12 and -32 days respectively for temperature, absolute humidity and solar radiation. Epidemic weeks were predicted accurately with the linear discriminant analysis method; however there were many misclassifications about intermediate and non-epidemic weeks. Transition probability to an epidemic state was 100% when meteorological variables were below: 2°C, 4 g/m3 and 32 W/m2, respectively for temperature, absolute humidity and solar radiation. This probability was 0% when meteorological variables were above: 6°C, 5.8g/m3 and 74W/m2.


CONCLUSIONS
These results confirm a good correlation between influenza-associated hospitalizations, meteorological factors and general practitioner's activity, the latter being the strongest predictor of hospital activity.
Service de Santé publique et d'information médicale, Centre Hospitalo-Universitaire, Saint-Etienne, France.
Radia
http://orcid.org/0000-0002-3146-4129
R
Spiga
Ecole Nationale Supérieure des Mines, Unité Mixte de Recherche 6158, Institut Fayol, Saint-Etienne, France.
Mireille
M
Batton-Hubert
Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 1136, Paris, France.|Sorbonne Universités, Université Pierre et Marie Curie Paris 06, Paris, France.|Centre Ingénierie et Santé, Ecole Nationale Supérieure des Mines, Saint Etienne, France.|Département d'Information Médicale, Centre Hospitalier, Firminy, France.
Marianne
M
Sarazin
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D058872:Epidemics / Q000706:statistics & numerical data*; D005260:Female; D005602:France / Q000453:epidemiology; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D006813:Humidity; D007223:Infant; D007231:Infant, Newborn; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D008297:Male; D008390:Markov Chains; D008875:Middle Aged; D015233:Models, Statistical; D025341:Principal Component Analysis; D012621:Seasons; D019445:Solar Activity; D013696:Temperature