Flooding and malaria in the Sahara: description of the 2024 outbreak in the Kidal region, Mali

Context During the 2024 rainy season, extreme rainfall events caused flooding in Mali, leading to an outbreak of malaria in the Kidal region of northern Mali. The aim of this study was to describe this epidemic and the response implemented by the national and regional authorities.

Weekly rainfall data (0.25° resolution) from TRMM and malaria cases from national health system. Data on SMCs and mobile clinics come from the national malaria control program. Malaria incidence and rainfall trends were analyzed, with the epidemic described according to severity and age group. The effects of the intervention were assessed using interrupted time series with a generalized additive model.

Rainfall began in week 25 (June) and lasted 15 weeks, averaging 3.86 mm/day (CI95: 3.23–4.57). The malaria epidemic began in week 30, peaked at 1,014 cases in week 39, and lasted 28 weeks (incidence: 1.688/1,000 person-weeks; CI95: 1.687–1.690). The [0-11] months and [1-4] years age groups were the most affected, with respective incidences of 1.48 and 0.97 per 1000 person-weeks for severe cases, and 5.04 and 2.35 per 1000 person-weeks for uncomplicated cases. Two interventions were implemented: i) 2 SMC campaigns among children aged 0 to 4 years for the first round, and 0 to 10 years for the second round, during weeks 31 (July) and 41 (October) respectively (6,236 and 27,334 children respectively); ii) mobile teams deployed from week 34 (August) to 39 (September) in remote areas and Internally Displaced People (IDP) sites, with 35 members in addition to the 36 community health workers. These interventions significantly reduced morbidity, with respective SIRs of 0.5 CI95[0.33; 0.75] (p=0.002) and 0.48 CI95[0.28; 0.82] for SMC and mobile teams.

Climate change is increasing extreme weather events like floods, altering malaria risk in unstable areas such as northern Mali. Preparedness should include reinforcing community health workers, ensuring adequate diagnostic and treatment stocks, and deploying targeted mobile teams. Competing Interest Statement The authors have declared no competing interest. Funding Statement The author(s) received no specific funding for this work. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study has been authorized by the competent authority, the Programme National de Lutte contre le Paludisme (number 108/MSDS-SG/PNLP, February 05, 2025), in accordance with Malian regulations on ethics and medical research. We also have the favorable opinion of the Ethics Committee of Aix-Marseille University (File Ref. No: 2025-03-13-88 01/DPO 760100). We also have an attestation of non-applicability of protective legislation on personal data from the General Data Protection Regulation (RGPD) team at Aix-Marseille. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data availability I have attached a supplementary file with associated information used in the manuscript.