[1] Malawi Liverpool Wellcome Trust Clin Res Program, Blantyre, Malawi
[2] Univ Malawi, Dept Paediat, Coll Med, Blantyre, Malawi
[3] Univ Liverpool, Royal Liverpool Childrens Hosp, Div Child Hlth, Liverpool L69 3BX, Merseyside, England
[4] Univ Liverpool, Div Med Microbiol, Liverpool L69 3BX, Merseyside, England
[5] Manchester Royal Infirm, Hlth Protect Agcy, Manchester Med Microbiol Partnership, Manchester M13 9WL, Lancs, England