Resurgence of malaria in the Amhara Region, Ethiopia (2014-2024): trends, spatial expansion, and control challenges.

BACKGROUND: Despite substantial control gains over the past 2 decades, malaria remains a major public health threat in Ethiopia. The Amhara Region has recently experienced a significant resurgence, threatening to reverse previous progress. However, comprehensive analyses of this resurgence integrating long-term trends, parasite species dynamics, and spatiotemporal patterns are limited. Therefore, this study examines trends, spatial expansion, and control challenges associated with malaria resurgence in the Amhara Region. METHODS: A retrospective analysis of 11 years (January 2014-December 2024) of weekly malaria surveillance data from 166 districts in the Amhara Region, Ethiopia. Joinpoint regression was employed to detect significant temporal trend changes. A resurgence threshold was defined a priori as a ≥ 20% increase in cases compared to the 3-year average baseline for the same period (Sep-Dec 2021-2023), based on an expert consensus survey. Auto-regressive integrated moving average modelling was used to characterize and forecast the test positivity rate (TPR). The Getis-Ord Gi* statistic was used to identify spatial clustering and detect transmission hotspots. RESULTS: During the study period, 7,710,733 malaria cases and 162 deaths were reported. Adults (≥ 15 years) contributed 62% of cases. A single trend inflection point occurred in late 2018, marking a shift from a significant decline (Annual Percent Change [APC]: -13.2%) to a sharp resurgence (APC: + 12.6%, 2018-2024). The Annual Parasite Incidence (API) rose from 10.9 (95% CI 10.8-11.0) per 1000 in 2018 to 74.8 (95% CI 74.72-74.93) per 1000 in 2024. Plasmodium vivax became increasingly prominent, with its contribution to the total case burden rising from 25 to 43% (χ2 = 190,789.55, p < 0.001). Its incidence surged 11-fold between 2018 and 2024 (from 2.7 to 32.4 per 1000). TPR increased from 10% (2018) to > 50% during peak months by 2024. In 2024, a resurgence occurred in 83% of districts; hotspots expanded into urban centres and previously low-transmission highland areas. CONCLUSION: The Amhara Region is experiencing a malaria resurgence characterized by intensified transmission, geographic expansion into urban and highland areas, and a significant shift toward Plasmodium vivax dominance. These findings exemplify an "elimination-resurgence paradox," where prior success increases vulnerability to threats such as invasive vectors, conflict, and climate shifts.