[1] Glasgow Caledonian Univ, Glasgow G4 0BA, Lanark, Scotland
[2] Hlth Protect Scotland, Glasgow G2 6QE, Lanark, Scotland
[3] Burnet Inst, Melbourne, Vic, Australia
[4] Monash Univ, Sch Publ Hlth & Prevent Med, Melbourne, Vic 3004, Australia
[5] Univ New S Wales, Kirby Inst Infect & Immun Soc, Sydney, NSW, Australia
[6] Alfred Hosp, Infect Dis Unit, Melbourne, Vic, Australia