We are studying the relationship between nutritional deficiencies and childhood infection using genetic and epidemiological approaches. This will help us to understand pathways to improve nutrition and prevent infection. This includes investigating the theoretical causal effects of malaria on iron deficiency, an effect likely to be mediated by hepcidin. We are also testing the theory that iron/vitamin D status may influence the risks of severe malaria and bacteraemia using genetic approaches. In addition, we are conducting the first genome-wide association studies of iron and vitamin D status in Africa. Validated genetic variants will be taken forward to large case-control studies of severe malaria and bacteraemia with the aim of targeting interventions to reduce infection.