[1] Bayero Univ, Dept Med, Aminu Kano Teaching Hosp, Kano 700241, Nigeria
[2] Bayero Univ, Africa Ctr Excellence Populat Hlth & Policy ACEPH, Kano, Nigeria
[3] Vanderbilt Univ, Ctr Med Hlth & Soc, 300 Calhoun Hall, Nashville, TN 37240 USA
[4] Ahmadu Bello Univ, Teaching Hosp, Dept Pediat, Zaria, Nigeria
[5] North Devon Dist Hosp, Barnstaple EX31 1NR, England
[6] Vanderbilt Inst Global Hlth, 2525 West End Ave,Suite 725, Nashville, TN 37203 USA