IL1B and malaria: For the meta-analysis of the difference in mean of IL-1β levels between severe malaria and uncomplicated malaria, the funnel plot was asymmetric (Additional file 3: Fig. S3); Egger’s test demonstrated no small-study effects (P = 0.07) and contour-enhanced funnel plot demonstrated the distribution of the MDs in both significant and non-significant areas (Additional file 4: Fig. S4), indicating that funnel plot asymmetry was due to other causes, such as heterogeneity of the MDs in the included studies, rather than publication bias.