Additional file 4. Overlapping of malaria transmission hotspots detected in 2012 with those detected in 2013. Empty cells indicates no intersection and no overlapping was observed i.e. d > R + r. A ratio = 1 indicates a total overlapping i.e. d = 0 and R = r, or d < R - r, where d is the distance between the centres of two given hotspots, R and r the radii of these hotspots. HS index hotspot index in relation to Additional file 8.