The four variables with a p-value < 0.2 in the bivariate analysis were age below 51 (p = 0.02), female sex (p = 0.03), HCW (p = 0.03) and smoking (p = 0.12). In the multivariate model (n = 850) all except female sex (p = 0.054) were significant, and the effect of smoking became statistically significant. Age below 51 (OR 1.44, p = 0.04), female sex (OR 1.36, p = 0.05) and HCW status (OR 1.34, p = 0.04) had an OR above 1, and smoking had an OR below 1 (OR 0.72, p = 0.04). Figure 3 shows the distribution of dates of onset for all SCII where an episode of ARI or ILI was reported.