Title : The role of contact tracing in the timely identification of cases in the 2022 Ebola outbreak in Uganda
Background: Contact tracing (CT) can support Ebola Virus Disease (EVD) outbreak control, but its effectiveness depends on rapid identification and regular, close monitoring of contacts. Ideally, all new cases should be previously-known contacts and spend minimal time ill in the community. After declaring an EVD outbreak on September 20, 2022, the Uganda Ministry of Health rapidly initiated CT. We assessed the performance of CT for EVD in Uganda during September 20-November 2, 2022.
Methods: We collated anonymized data from the national EVD line list, contacts database, and paper CT forms to obtain data on key variables. An EVD-confirmed case had a positive RT-PCR laboratory result for Ebola virus. We calculated the proportion of cases listed as contacts before lab confirmation by epidemic week. The Mann-U Whitney test was used to compare time from onset to isolation among cases who were previously listed and those who were not. We calculated odds ratios for confirmed cases having been listed as a contact before confirmation by area (urban/rural, classified at subcounty level) and a number of health facilities visited before confirmation.
Results: In total, 131 cases and 2,966 contacts were identified between September 20 and November 2, 2022. Overall, 31% of cases were listed as contacts before lab confirmation; this increased from 7% (3/44) in epi weeks 38 to 40 (first weeks of the outbreak) to 42% (37/87) in epi weeks 41 to 44. Cases previously identified as contacts had fewer median days from onset to isolation (2 versus 4; p<0.01) than cases not previously identified as contacts. The odds of being listed as a contact before identification as a case were 71% lower among cases from rural versus urban areas (OR=0.29, 95%CI: 0.11-0.76). Cases not previously listed as contacts had 4 times (OR:3.6,95% CI:1.6-8.1) higher odds of visiting ≥2 health facilities than those who were previously listed.
Conclusion: CT reduced the time EVD cases spent in the community before isolation and number of health facilities visited before confirmation in Uganda. However, contact listing was less successful with rural than urban contacts. Improved contact tracing in rural areas my require new or modified approaches.
Keywords: Contact tracing, Case Identification, Ebola Virus Disease
Audience take away:
The role of contact tracing in controlling infectious disease outbreaks remains poorly understood with varied results in different settings. This presentation shares experiences and the role of contact tracing in controlling the 2022 Ebola Virus Disease Outbreak. From this presentation, the audience will learn best practices in establishing contact tracing and how it can be used to retain EVD outbreaks.