[1] Imperial Coll London, Sch Publ Hlth, Dept Infect Dis Epidemiol, Fac Med, London, England
[2] Imperial Coll London, MRC Ctr Global Infect Dis Anal, London, England
[3] UCL, UCL Inst Risk & Disaster Reduct, Fac Math & Phys Sci, London, England
[4] UCL, UCL Inst Global Hlth, Fac Populat Hlth Sci, London, England
[5] Univ Agder, Kristiansand, Norway
[6] London Sch Hyg & Trop Med, MRC Unit Gambia, Fajara, Gambia