[1] Univ Bristol, Bristol Med Sch, Populat Hlth Sci, Bristol, England
[2] Univ Manitoba, Ctr Global Publ Hlth, Winnipeg, MB, Canada
[3] Ctr Global Publ Hlth, Canada Pakistan HIV AIDS Surveillance Project, Islamabad, Pakistan
[4] JC Wilt Infect Dis Res Ctr, Natl HIV & Retrovirol Labs, Publ Hlth Agcy Canada, Winnipeg, MB, Canada
[5] Univ Manitoba, Dept Med Microbiol & Infect Dis, Winnipeg, MB, Canada
[6] Publ Hlth Agcy Canada, Ctr Communicable Dis & Infect Control, Ottawa, ON, Canada
[7] Univ Bristol, Bristol Med Sch, Populat Hlth Sci, Oakfield House,Oakfield Grove, Clifton BS8 2BN, England