[1] Imperial Coll London, Dept Infect Dis, London, England
[2] Imperial Coll London, NIHR Hlth Protect Res Unit Healthcare Associated, London, England
[3] Univ Cambridge, Dept Vet Med, Cambridge, England
[4] Concord Hosp, Dept Microbiol & Infect Dis, Sydney, NSW, Australia
[5] George Washington Univ, Milken Inst Sch Publ Hlth, Washington, DC USA
[6] Univ Tromso, Dept Med Biol, Fac Hlth Sci, Tromso, Norway