Dengue outbreak Investigation tool.

Background

Since 2013, dengue cases have shown a marked increase in Ethiopia. The current suspected outbreak occurring in Metahara town, Oromia Regional State, began in July 2023. This study aimed to confirm and characterize the outbreak, identify risk factors, and implement control measures.

Methods

We conducted a descriptive study and an unmatched case-control design, using a one-to-two ratio of cases to controls. We collected data on the dengue outbreak using line lists, laboratory test results, environmental observations, home visits, and entomological examinations. We selected a total of 50 cases using simple random sampling from the line list and purposively chose 100 controls from the same block. We applied community-based face-to-face interviews with 150 participants. After gathering data through Kobo Collect, we analyzed it using Statistical Package for the Social Sciences (SPSS) version 26 and summarized the findings in Microsoft Excel 2013. A binary logistic regression model was employed to identify significant variables, with p-values ≤ 0.25 in bivariate analysis considered for the final model. Crude and adjusted odds ratios (OR and AOR) were used to measure associations, with p-values ≤ 0.05 indicating significance.

Results

The investigation confirmed 342 dengue cases, corresponding to an attack rate of 7.1 per 1,000 population and a case fatality rate of 0.88%. Significant risk factors included not using long-lasting insecticide nets during the daytime (9-fold increased likelihood) and having open water containers (5-fold increased likelihood. Respondents lacking disease awareness were 25 times more likely to be infected, while wearing long-sleeved clothing conferred a protective effect of 75% reduction in risk.

Conclusion

The dengue outbreak in Metahara town was driven by epidemiological, entomological, and environmental factors, with Aedes aegypti as the primary vector. The ongoing circulation of DENV-3, coupled with insufficient vector control measures, poses a serious public health threat. Key contributing factors to the outbreak include the lack of utilization of long-lasting insecticide nets (LLINs) during the daytime, improper water storage practices, insufficient public knowledge regarding transmission and prevention strategies, and inadequate protective clothing choices that increase vulnerability to mosquito bites. Strategies including vector control, community education, promotion of protective clothing, and improved surveillance were recommended.