Conflict of interest: None declared.
Authors’ contributions: PYB, VC, CP, CS, TB designed the study. PYB, CS, TL analysed the data. CG, CT, TH contributed data on incidence. SB, VE, BL, SVDW characterised viruses. PYB drafted the manuscript. BL, SVDW, DLB contributed to the manuscript. All authors approved the last version.