Investigation of, and strategies to control the final cluster of the 2018-2020 Ebola virus disease outbreak in eastern Democratic Republic of Congo

Background On April 10, 2020, while the independent committee of the International Health Regulation (IHR) was meeting to decide whether the 10th Ebola outbreak in the DRC still constituted a Public Health Emergency of International Concern, a new confirmed case was notified in the city of Beni, the last epicentre of the epidemic. This study aimed to understand the source of this cluster and learn from the implemented control strategies for improved EVD outbreak response in future.   Methods We conducted a combined epidemiological and genomic investigation to understand the origins and dynamics of transmission within this cluster and describe the strategy that successfully controlled the outbreak.    Results Eight cases were identified as belonging to the last cluster of Beni; two males and six females, with a median age of 22 years (range 7 - 68 years). Five cases were likely nosocomially infected. A total of 1,028 contacts were identified. Whole Genome Sequencing revealed that all cases belonged to the same cluster, the closest sequence to which was identified as a case from Beni area with symptom onset in July 2019 and a difference of just 31 nucleotides. Outbreak control measures included community confinement of high-risk contacts, undertaken in accordance with key guiding principles agreed with the affected community.   Conclusion The study illustrates the high risk of additional flare-ups in the period leading to the end-of-outbreak declaration and the importance of maintaining enhanced surveillance and confinement activities to rapidly control Ebola outbreaks.