Mortality surveillance implementation to identify transmission chains during the Sudan virus disease outbreak in Masaka, Uganda, 2022

Introduction: Six weeks into the Sudan Virus Disease (SVD) outbreak response in Uganda, Masaka City registered a case on November 1st, 2022. We describe the design of mortality surveillance implemented to ensure no transmission chains were missed and epidemiologically characterise deaths reported. Methods: Similar to other SVD epicentre districts (Mubende, Kassanda, and Kampala) in Uganda, health workers, Village Health Teams, security, and other local structures were trained in death reporting. Records at 33 health facilities in Masaka City and District were reviewed, and an alert desk was activated. Upon receiving a death alert, laboratory and surveillance officers were dispatched to investigate deaths and collect samples (arterial blood or buccal swab) from cadavers for Sudan Virus testing. A death-linelist was populated by sociodemographics, date of death, source of alert, and test result. We conducted a descriptive analysis of deaths. Results: Between November 10th and December 30th 2022, 268 deaths were reported, 90% had samples collected, and none (0%) tested positive for SVD. Median age at death was 45 years (IQR: 28-68), and the age group 25-49 years (30%) recorded most deaths. Males (170, 63%) were more affected than females (87, 32%) (p<0.001). Community (137, 51%) and facility deaths (131, 49%) (p=0.74) were comparable. Thirty eight percent (101 of 268) had cause of death documented. Leading causes of death were accidents and injuries (27%), cardiovascular (16%), respiratory (12%) and perinatal conditions (9%). Natural causes of death (21% [15 of 73] were more prevalent among individuals aged 65-79 years vs unnatural causes (3.6% [1 of 28]; p<0.03). Unnatural causes were more prevalent among the age group 25-49 years (57% [16 of 28] compared to natural causes 16% [12 of 73]; p<0.0001). Conclusion: No secondary transmission of SVD occurred; instead, individuals died of other causes. It is feasible to conduct mortality surveillance during an SVD outbreak to rule out silent transmission. We recommended strengthening mortality surveillance at the local and national levels to improve epidemic surveillance and response.