For each study we worked out case fractions for malaria IBI co-infection as ‘number of children with malaria AND IBI’ (numerator) divided by ‘number of children with malaria’ (denominator). We used the Q test, as a measure of heterogeneity among studies, calculated as the weighted sum of squared differences between individual study effects and the pooled effect across studies. I2 was calculated to quantify heterogeneity (between-studies variability) [7]. Since the definitions for SM vary from study to study, we also compared the study inclusion criteria for SM cases with the WHO definition of SM [8].