Epidemiological investigation of a possible malaria outbreak in Arba Minch town, Gamo Zone, Southern Ethiopia, 2023.

BACKGROUND: Malaria remains a major public health concern in Ethiopia, particularly in endemic settings like Arba Minch Town, where environmental and behavioural factors contribute to persistent malaria epidemic. Despite ongoing control efforts, malaria remains a substantial morbidity, mortality, and socio-economic disruption. The objective of the study was to examine epidemiological investigation of a possible malaria outbreak and risk factors in Arba Minch Town, Gamo Zone, Southern Ethiopia, 2023. METHODS: A descriptive epidemiological analysis was followed by a 1:1 unmatched community-based case-control study conducted from October 28, 2022, to December 28, 2023. Ninety-four rapid diagnostic test-confirmed cases and 94 neighbourhood controls were selected. Data were collected through structured questionnaires. Data were collected and entered into Epi Info 7.2.6, and then exported to the Statistical Package for the Social Sciences (SPSS) version 26 for statistical analysis. Bivariable logistic regression was conducted, and candidate variables (p-value ≤ 0.25) were selected for multivariable logistic regression analysis. The degree of the association was assessed by computing the adjusted odds ratio (AOR) with a 95% confidence interval (CI). Statistical significance was determined for variables in the final models with p-values < 0.05. RESULTS: A total of 5181 confirmed malaria cases were reported, with a positivity rate of 22.7% and an attack rate of 41.2 per 1000 population. Plasmodium falciparum accounted for 71% of infections, with the outbreak peaking in epidemiological week 3 of 2023. Significant risk factors included residence proximity to mosquito breeding sites [AOR = 5.45; 95% CI 2.11-14.08], presence of stagnant water [AOR = 5.69; 95% CI 2.22-14.55], poor housing [AOR = 4.40; 95% CI 1.83-10.54], inconsistent utilization of long lasting insecticidal nets (LLIN) [AOR = 0.30; 95% CI 0.13-0.71], and poor knowledge [AOR = 0.04; 95% CI 0.02-0.12]. CONCLUSION: The long-term malaria epidemic was primarily driven by P. falciparum. Poor housing, environmental conditions, inadequate LLIN distribution and inconsistent utilization, and knowledge of the malaria transmission and prevention were the predicting factors. Improving vector control, environmental management, community education, and robust surveillance are crucial to reduce the long period of malaria outbreaks.