Yellow fever outbreak investigation potentially linked to zoonotic spill over in Eastern Uganda, April-July 2024

Abstract

Introduction: Uganda has reported numerous yellow fever outbreaks in the past decade. Despite the rollout of control interventions such as vaccination, recurrent outbreaks continue to occur. This paper describes the yellow fever outbreak investigation in Ngora district, Uganda. Methods: This was a descriptive outbreak investigation. We defined a suspected case of yellow fever as a resident or visitor of Ngora district who reported onset of unexplained fever (negative for malaria, or non-responsive to malaria treatment, and not explained by any other known reasons) from April to July 2024, plus two or more symptoms such as unexplained jaundice, abdominal pain, or headache that could not be explained by other causes. A confirmed case was a suspected case with laboratory confirmation of yellow fever-specific neutralising antibodies using the plaque reduction neutralisation test. Confirmed cases were identified through a review of records of twenty suspected cases reported between April and July 2024 at the sentinel surveillance site. A standardized case investigation form was used to collect information on exposures. We computed proportions to describe characteristics of the cases, and reviewed records to determine vaccination coverage in the district. Data were analysed using STATA v16. Results: Five confirmed cases of yellow fever were identified. Four were female, with an age range of 5-49 years. The fifth case resulted in a fatality; thus, no data was collected. One case had a previous history of vaccination. Fatigue (75%, n=3), muscle and joint pain (75%, n=3) and headache (75%, n=3) were the most commonly reported signs and symptoms. Three cases (75%) reported previous contact with animals, among which were monkeys. Conclusion: This yellow fever outbreak was potentially linked to a zoonotic spillover. This study highlights the urgent need for targeted one health interventions, such as integrated vector control, aimed at controlling yellow fever and other zoonoses within the district.