Fig. 5
Investigating the drivers of the temporal variability in COVID-19 hospitalisation incidence. Each density plot reports the distribution of correlation values obtained when comparing daily hospitalisation ratios (DHRs) and a specific temporal covariate for the entire epidemic period under consideration (01/03–30/11/20). Each reported distribution gathers 103 correlation values, i.e. one correlation value (Spearman) per hospital catchment area (HCA). In addition, we also report one distribution per lag time considered for estimating the correlation between DHRs and the considered temporal covariate. In practice, we investigated lag times ranging from 1 to 30 days. PM2.5 refers to particle matters ≤ 2.5 μm