GSTM1 and malaria: Each week, trained MRC field assistants (FA) will invite the study participants to a central location within their communities for collection of a finger prick blood sample for analysis of haemoglobin (Hb) using a HemoCue Hb 301 analyser (HemoCueAB, Angelholm, Sweden), malaria parasitaemia using a SD Bioline One step malaria antigen Pf Test (SD Standard Diagnostics, Inc. Kyonggi-do, Korea) and hepcidin levels using the BACHEM Hepcidin-25 ELISA.