Sudan virus disease super-spreading, Uganda, 2022

Abstract Background: On September 20, 2023, Uganda declared its 5th Sudan virus disease (SVD) outbreak, culminating in 142 confirmed and 22 probable cases. The reproductive rate (R) of this outbreak was 1.25. We describe persons to whom exposure resulted in an unusual number of cases during the outbreak. Methods: We defined a super-spreader person (SSP) as any person with RT-PCR-confirmed SVD linked to infection of ≥13 other persons (10-fold the outbreak R). We reviewed illness narratives for SSPs collected through interviews. Whole-genome sequencing was used to support epidemiologic linkages between cases. Results: Two SSPs were identified (Patient A, a 33-year-old male, and Patient B, a 26-year-old male), linked to one probable and 50 confirmed secondary cases. Both SSPs lived in the same parish and were likely infected by a single ill healthcare worker in early October while receiving healthcare. Both sought treatment at multiple health facilities, but neither was ever isolated at an Ebola Treatment Unit (ETU). In total, 18 secondary cases (17 confirmed, 1 probable), including 3 deaths (17%), were linked to Patient A; 33 secondary cases (all confirmed), including 14 (42%) deaths, were linked to Patient B. Secondary cases linked to Patient A included family members, neighbours, and contacts at health facilities, including healthcare workers; those linked to Patient B included healthcare workers and friends and family who interacted with him throughout his illness, prayed over him while he was near death, or exhumed his body. Intensive community engagement and awareness-buildling was initiated based on narratives collected about patients A and B; 49 (96%) of the secondary cases were isolated in an ETU, a median of 3 days after onset. Only nine tertiary cases were linked to the 51 secondary cases. Sequencing suggested plausible direct transmission from the SSPs to 37 of 39 secondary cases with sequence data. Conclusion: Extended time in the community while ill, social interactions, cross-district travel for treatment, and religious practices contributed to SVD super-spreading. Intensive community engagement and awareness may have reduced the number of tertiary infections. Intensive follow-up of contacts of case-patients detected late in infection may help reduce the impact of super-spreading events.