Epidemiological, Entomological, and Climatological Investigation of the 2019 Dengue Fever Outbreak in Gewane District, Afar Region, North-East Ethiopia

SIMPLE SUMMARY: Dengue Fever (DF) is a viral disease transmitted by mosquitoes throughout tropical, sub-tropical, and some temperate climates worldwide. DF ranges in severity from mild flu-like symptoms to severe joint and muscle pain and even death from severe dengue. In the past 50 years, DF incidence has increased 30-fold, with 3.9 billion people in 129 countries currently considered at-risk annually. DF has been circulating on the African sub-continent for decades, but actual cases are highly under-reported due to their non-specific symptomology and overlapping distributions with other febrile illnesses, notably malaria and pneumonia. Ethiopia has been experiencing annual DF outbreaks since 2013. This study describes key epidemiological, entomological, and climatological features of the first DF outbreak in Gewane District, Afar Region, Ethiopia, in 2019. A total of 1185 DF cases were identified, mostly among individuals aged 15–49, experiencing fever, headache, and joint pain; there was no recorded death. Mosquito species that transmit DF (Aedes aegypti) were found breeding in plastic tanks, tires, and plastic or metal buckets/bowls in and around DF patients’ homes. High rainfall in July 2019 and long-term storage of uncovered, stagnant drinking water by community members were implicated in this outbreak. The study results emphasize the need for control activities targeting Ae. aegypti and improved entomological surveillance to prevent future DF outbreaks in this part of Ethiopia. ABSTRACT: Dengue Fever (DF) is an important arthropod-borne viral infection that has repeatedly occurred as outbreaks in eastern and northeastern Ethiopia since 2013. A cross-sectional epidemiological outbreak investigation was carried out from September to November 2019 on febrile patients (confirmed malaria negative) who presented with suspected and confirmed DF at both public and private health facilities in Gewane District, Afar Region, northeastern Ethiopia. Entomological investigation of containers found in randomly selected houses belonging to DF-positive patients was undertaken to survey for the presence of Aedes larvae/pupae. A total of 1185 DF cases were recorded from six health facilities during the 3-month study period. The mean age of DF cases was 27.2 years, and 42.7% of cases were female. The most affected age group was 15–49 years old (78.98%). The total case proportions differed significantly across age groups when compared to the population distribution; there were approximately 15% and 5% higher case proportions among those aged 15–49 years and 49+ years, respectively. A total of 162 artificial containers were inspected from 62 houses, with 49.4% found positive for Aedes aegypti larva/pupae. Aedes mosquitoes were most commonly observed breeding in plastic tanks, tires, and plastic or metal buckets/bowls. World Health Organization entomological indices classified the study site as high risk for dengue virus outbreaks (House Index = 45.2%, Container Index = 49.4%, and Breteau Index = 129). Time series climate data, specifically rainfall, were found to be significantly predictive of AR (p = 0.035). Study findings highlight the importance of vector control to prevent future DF outbreaks in the region. The scarcity of drinking water and microclimatic conditions may have also contributed to the occurrence of this outbreak.