Analysis of clinical malaria hotspots according to transmission levels in two health areas of the Kolondieba health district, Mali

Background: Despite significant progress, malaria remains a major challenge in Mali, due to heterogeneous transmission. The WHO 'High Burden to High Impact' strategy advocates targeting of high-transmission areas. This study aimed to identify clinical malaria hotspots in two health areas within the Kolondieba district with differing transmission levels. Materials and Methods: A retrospective cross-sectional study analysed 35,934 confirmed malaria cases extracted from consultation registers between 2019 and 2021 in the health areas of Kadiana (high risk) and Kolondieba Central (moderate risk). Transmission periods were determined in each zone by analysing variations in mean incidence trends, and high-risk clusters (hotspots) were identified using Kulldorff's method according to these periods. Results: Transmission periods and hotspot identification (2019-2021) revealed distinct dynamics between the two health areas. In Kadiana, the majority of clusters remained stable, with persistent hotspots across all eight periods (Kadiana and Tienkourani; RR: 1.8-6.3). In Kolondieba Central, hotspot dynamics evolved from a localised configuration (1 to 2 villages) towards spatial expansion, with more extensive clusters appearing during the final periods (RR: 1.7-2.2). Kolondieba town remained a persistent hotspot. Conclusions: This study confirms the heterogeneity of transmission at a fine scale, with stable hotspots even in both moderate and high-risk areas. It is essential to focus on human mobility to guide malaria control interventions.