Quantifying the risk of nosocomial infection within Ebola Holding Units: a retrospective cohort study of negative patients discharged from five Ebola Holding Units in Western Area, Sierra Leone.

Objectives: A central pillar in the response to the 2014 Ebola virus disease (EVD) epidemic in Sierra Leone was the role of Ebola Holding Units (EHUs). These units isolated patients meeting a suspect case definition, tested them for EVD, initiated appropriate early treatment and discharged negative patients to onward inpatient care or home. Positive patients were referred to Ebola Treatment Centres. We aimed to estimate the risk of nosocomial transmission within these EHUs.

Methods: We followed up a cohort of 543 patients discharged with a negative EVD test from five EHUs in the Western Area, Sierra Leone, and examined all line-listed subsequent EVD tests from any facility in the Western Area to see whether the patient was retested within 30 days, matching by name, age and address. We defined possible readmissions as having the same name and age but uncertain address, and confirmed readmissions where name, age and address matched.

Results: We found a positive readmission rate of 3.3% (18 cases), which included 1.5% confirmed readmissions (8 cases) and 1.8% possible readmissions (10 cases). This is lower than rates previously reported. We cannot ascertain whether EVD was acquired within the EHUs or from re-exposure in the community. No demographic or clinical variables were identified as risk factors for positive readmission, likely due to our small sample size.

Conclusions: These findings support the EHU model as a safe method for isolation of suspect EVD patients and their role in limiting the spread of EVD.