Malaria epidemics and its drivers in Uganda in 2022

(2025) 24:235 Aregawi et al. Malaria Journal https://doi.org/10.1186/s12936-025-05351-4 Malaria Journal Open Access RESEARCH Malaria epidemics and its drivers in Uganda in 2022 Maru W. Aregawi1*, Catherine Maiteki2, John C. Rek2, Bosco Agaba2,5, Charles Katureebe3, Mansour Ranjbar3, Chunzhe Zhang1, Samson Kiware4† and Jimmy Opigo2† Abstract Background In Uganda, malaria is a year-round health threat, with transmission intensity varying across regions. Despite ongoing intensified interventions, an unprecedented malaria resurgence in early 2022 affected several districts, prompting a swift response from the National Malaria Control Division (NMCD). This study aims to assess the scale and underlying causes of the epidemics, quantify the excess cases and deaths, and propose targeted prevention and response strategies. Methods District Health Information System (DHIS2) data from 2017 to 2022 were analysed. A 75th percentile threshold from 2017 to 2021 was used to define true malaria epidemics and compare them to the suspected 2022 epidemic. Excess cases, admissions, and deaths were quantified using area under the curve (AUC) calculations. The level of epidemics was compared across districts with Indoor Residual Spraying (IRS) and Integrated Community Case Management (iCCM) interventions. Precipitation data from multiple sources were used to evaluate rainfall patterns and their impact on malaria epidemics. Results Malaria cases were lowest in 2018 but rose by 31% in 2022 compared to the 2017–2021 3rd quartile. Sixty-four of 146 districts experienced epidemics, with 4 facing persistent epidemics year-round. The 2022 epidemic accounted for 3,379,309 (95% CI 1,553,714, 5,339,709) total excess outpatient malaria cases (confirmed and presumed), 3,018,920 (95% CI 1,321,951, 4,661,201) excess confirmed cases, 149,789 (95% CI 66,029, 235,743) excess inpatient cases. Paradoxically, more epidemics occurred in IRS and iCCM districts. Precipitation patterns were consistent across years and were insignificantly correlated with the 2022 epidemic. Provinces with bimodal rainfall patterns were more prone to epidemics, while unimodal regions had fewer epidemics but higher incidence rates. Rainfall lagged by two months (Lag 2) significantly increased malaria incidence (p < 0.01), with each millimetre of rainfall two months prior associated with 13.4 additional malaria cases. Conclusion The 2022 malaria epidemic affected 64 districts, with over 3.3 million excess cases and nearly 150,000 excess admissions. Gaps in IRS, iCCM, and intervention coverage, along with minimal rainfall correlation and high vulnerability in bimodal regions, highlight the need for better surveillance, sustainable funding, and tailored responses. While climate was not the main driver, programmatic deficiencies, vector composition shift, reduced efficacy of insecticides, coverage and effectiveness of the interventions likely fueled the epidemic. Strengthening epidemic preparedness, response, and investment will be crucial to preventing future outbreaks and achieving long-term malaria control in Uganda. † Samson Kiware and Jimmy Opigo have contributed equally to this work. *Correspondence: Maru W. Aregawi Full list of author information is available at the end of the article © The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/. Aregawi et al. Malaria Journal (2025) 24:235 Background Uganda consists of 146 administrative districts with an approximate population of 48.6 million in 2022 [1]. Malaria transmission occurs year-round and varies in intensity and parasite prevalence among regions characterized by bimodal and unimodal rainy seasons. Over a period of continuous investment and intervention efforts, the prevalence of parasites in the country has significantly decreased. The national average parasite prevalence dropped from 42% in 2009 [2] to 19% in 2014 [3], and further down to 9% in 2019 [4]. However, variations exist across different regions. The Karamoja region has the highest prevalence at 34.3%, followed by West Nile at 21.8%, and Busoga at 21.1%. Conversely, Kampala exhibits the lowest prevalence at just 0.2% [5]. The main malaria vectors in Uganda are Anopheles gambiae sensu stricto (s.s.), Anopheles funestus, and Anopheles arabiensis. The majority of reported infections confirmed with Rapid Diagnostic Tests (RDT) and microscopy are caused by Plasmodium falciparum (98%), while a small portion involves mixed infections with Plasmodium ovale and Plasmodium malariae. Molecular studies showed increased non-falciparum and mixed malaria infections, especially in those over 5 years of age [6]. The Uganda Malaria Reduction and Strategic Plans (UMRSP) 2014–2020 and 2021–2025, outline a mix of interventions for maximum impact across various epidemiological settings. Main vector control interventions included the distribution of Long-Lasting Insecticidal Nets (LLINs) and Indoor Residual Spraying (IRS). The government and its partners distributed 28.4 million LLINs from November 2020 to March 2021, achieving a 90% administrative coverage. No recent household surveys have been available since 2019 to inform latest community-level LLIN ownership. Campaigns targeted both urban and rural areas and were supplemented by continuous distribution through Antenatal care (ANC), Expanded Programme for Immunization (EPI), and schools. A post-campaign study found that 93.4% of households owned at least one LLIN, with 56.8% of households had one LLIN for two persons, and 71% of the residents sleeping under LLIN the previous night [7]. In Uganda’s malaria reduction strategic plan, IRS complements LLINs by targeting high-burden districts. Initially introduced in high-transmission areas, IRS from targeted districts is gradually phased out as malaria prevalence decreases, while LLINs continue to provide protection. Because of funding issues, the number of IRS/districts fluctuated between 10 and 16 districts during 2009–2022. IRS was initiated in 10 district (...truncated)