[1] Univ Laval, Ctr Rech, CHU Quebec, Axe Sante Populat & Prat Optimales Sante, Quebec City, PQ, Canada
[2] CHUM, Ctr Rech, Montreal, PQ, Canada
[3] Inst Natl Sante Publ Quebec, Quebec City, PQ, Canada
[4] Imperial Coll, Dept Infect Dis Epidemiol, London, England