Ebola disease outbreak caused by the Sudan virus in Uganda, 2022: a descriptive epidemiological study

Abstract

Background: Uganda has had seven Ebola disease outbreaks, between 2000 and 2022. On Sept 20, 2022, the Ministry of Health declared a Sudan virus disease outbreak in Mubende District, Central Uganda. We describe the epidemiological characteristics and transmission dynamics.

Methods: For this descriptive study, cases were classified as suspected, probable, or confirmed using Ministry of Health case definitions. We investigated all reported cases to obtain data on case-patient demographics, exposures, and signs and symptoms, and identified transmission chains. We conducted a descriptive epidemiological study and also calculated basic reproduction number (R_o) estimates.

Findings: Between Aug 8 and Nov 27, 2022, 164 cases (142 confirmed, 22 probable) were identified from nine (6%) of 146 districts. The median age was 29 years (IQR 20-38), 95 (58%) of 164 patients were male, and 77 (47%) patients died. Symptom onsets ranged from Aug 8 to Nov 27, 2022. The case fatality rate was highest in children younger than 10 years (17 [74%] of 23 patients). Fever (135 [84%] of 160 patients), vomiting (93 [58%] patients), weakness (89 [56%] patients), and diarrhoea (81 [51%] patients) were the most common symptoms; bleeding was uncommon (21 [13%] patients). Before outbreak identification, most case-patients (26 [60%] of 43 patients) sought care at private health facilities. The median incubation was 6 days (IQR 5-8), and median time from onset to death was 10 days (7-23). Most early cases represented health-care-associated transmission (43 [26%] of 164 patients); most later cases represented household transmission (109 [66%]). Overall R_o was 1·25.

Interpretation: Despite delayed detection, the 2022 Sudan virus disease outbreak was rapidly controlled, possibly thanks to a low R_o. Children (aged <10 years) were at the highest risk of death, highlighting the need for targeted interventions to improve their outcomes during Ebola disease outbreaks. Initial care-seeking occurred at facilities outside the government system, showing a need to ensure that private and public facilities receive training to identify possible Ebola disease cases during an outbreak. Health-care-associated transmission in private health facilities drove the early outbreak, suggesting gaps in infection prevention and control.

Funding: None.

Figure 1

Previous Ebola disease outbreaks in Uganda, 2000–19 Years of the outbreak are indicated. Numbers indicate cases and numbers in parentheses indicate deaths. Note that the Ebola virus cases (2019) represented spillover from the Democratic Republic of the Congo in 2018, and that 2012 a and 2012 b are two separate outbreaks that occurred in the same year.

Figure 2

Cases by illness onset and case classification (n=164) in Uganda, Aug 8–Nov 27, 2022 Four cases without onset dates have been included by their date of laboratory confirmation and one case, which was a stillbirth, has been included by its date of birth (Nov 27).

Figure 3

Attack rates by district of residence in Uganda, August–November, 2022