[1] Biomed Res & Training Inst, Hlth Res Unit Zimbabwe, Harare, Zimbabwe
[2] London Sch Hyg & Trop Med, Fac Epidemiol & Populat Hlth, Infect Dis Epidemiol, London WC1E 7HT, England
[3] Monash Univ, Sch Clin Sci, Monash Med Ctr Nursing & Hlth Sci, Fac Med,Dept Med, Clayton, Vic 3168, Australia
[4] Univ Bristol Sch Med, Populat Hlth Sci, Bristol BS8 1NU, England
[5] Univ Southampton, MRC Lifecourse Epidemiol Ctr, Human Dev & Hlth, Southampton SO16 6YD, England
[6] London Sch Hyg & Trop Med, Fac Infect & Trop Dis, Clin Res Dept, London WC1E 7HT, England
[7] Gambia London Sch Hyg & Trop Med, MRC Unit, Banjul, Gambia
[8] Univ Bristol, Bristol Med Sch, Musculoskeletal Res Unit, Global Musculoskeletal Res Grp, Bristol BS10 5NB, England