Dengue Fever Outbreak Investigation in Werder Town, Dollo Zone, Somali Region, Ethiopia

Background: Dengue fever (DF) is a mosquito-borne disease caused by the dengue virus. DF is endemic to many tropical and subtropical countries around the world. In Ethiopia, DF emerged in 2013 and caused a serious public health problem. Objective: We investigated the outbreak to describe by time, place, person, and to identify risk factors associated with the outbreak in Methods: Descriptive and case-control studies (1:2 ratio) were conducted. We used the World Health Organization (WHO) case definition to identify cases in Werder town from December 10, 2020, to January 4, 2021. Controls were selected from the same town that did not suffer from DF. Serum samples were tested by reverse transcription polymerase chain reaction (RT-PCR) to detect the dengue virus and to identify serotypes. A structured questionnaire was used to collect socio-demographic, behavioural, and environmental characteristics. Results: We identified a total of 57 cases and 114 controls. The overall attack rate was 334.41/100,000 with a zero case fatality rate. Six out of twenty serum samples tested positive for the DEN-3 serotype. In multivariate analysis, not hearing of DF (Adjusted odd ratio (AOR): 2.2, 95% CI: 1.015-4.701), not knowing the mode of transmission (AOR: 2.9, 95% CI: 1.338-6.831), not using longlasting insecticidal net (LLITN) (AOR: 4.4, 95% CI: 1.592-12.330) and not spraying insecticide (AOR: 3.6, 95% CI: 1.591-8.098) were statistically significant risk factors associated with DF outbreak. However, wearing long sleeves (AOR: 0.435, 95% CI: 0.206- 0.918) was a protective factor for the DF outbreak. Conclusion: DF outbreak in Werder town has been confirmed. The present study provides evidence-based information regarding the identified risk factors that have contributed to the occurrence of DF outbreaks. We recommended implementing vector control measures and strengthening dengue surveillance systems is strongly advised.