title: Contact tracing performance during the Ebola virus disease outbreak in Kenema district, Sierra Leone.
abstract: Contact tracing in an Ebola virus disease (EVD) outbreak is the process of identifying individuals who may have been exposed to infected persons with the virus, followed by monitoring for 21 days (the maximum incubation period) from the date of the most recent exposure. The goal is to achieve early detection and isolation of any new cases in order to prevent further transmission. We performed a retrospective data analysis of 261 probable and confirmed EVD cases in the national EVD database and 2525 contacts in the Contact Line Lists in Kenema district, Sierra Leone between 27 April and 4 September 2014 to assess the performance of contact tracing during the initial stage of the outbreak. The completion rate of the 21-day monitoring period was 89% among the 2525 contacts. However, only 44% of the EVD cases had contacts registered in the Contact Line List and 6% of probable or confirmed cases had previously been identified as contacts. Touching the body fluids of the case and having direct physical contact with the body of the case conferred a 9- and 20-fold increased risk of EVD status, respectively. Our findings indicate that incompleteness of contact tracing led to considerable unmonitored transmission in the early months of the epidemic. To improve the performance of early outbreak contact tracing in resource poor settings, our results suggest the need for prioritized contact tracing after careful risk assessment and better alignment of Contact Line Listing with case ascertainment and investigation.This article is part of the themed issue 'The 2013-2016 West African Ebola epidemic: data, decision-making and disease control'.
authors.affiliation: Department of Pandemic and Epidemic Diseases, World Health Organization, Geneva, Switzerland sengam@who.int.
authors.forename: Mikiko
authors.identifier: http://orcid.org/0000-0003-3041-2236
authors.initials: M
authors.lastname: Senga
authors.affiliation: Kenema District Health Management Team, Kenema District, Sierra Leone.
authors.forename: Alpha
authors.initials: A
authors.lastname: Koi
authors.affiliation: Tulane University, New Orleans, LA 70112, USA.
authors.forename: Lina
authors.initials: L
authors.lastname: Moses
authors.affiliation: Consulting for Fondation Mérieux, 69002 Lyon, France.
authors.forename: Nadia
authors.initials: N
authors.lastname: Wauquier
authors.affiliation: Department of Global Capacities, Alert and Response, World Health Organization, Geneva, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Barboza
authors.affiliation: Global Outbreak and Alert Response Network (GOARN), World Health Organization, Geneva, Switzerland.|Pasteur Institute, BP220 Dakar, Senegal.
authors.forename: Maria Dolores
authors.initials: MD
authors.lastname: Fernandez-Garcia
authors.affiliation: World Health Organization, Sierra Leone Country Office, Freetown, Sierra Leone.
authors.forename: Etsub
authors.initials: E
authors.lastname: Engedashet
authors.affiliation: World Health Organization, Sierra Leone Country Office, Freetown, Sierra Leone.
authors.forename: Fredson
authors.initials: F
authors.lastname: Kuti-George
authors.affiliation: World Health Organization, Sierra Leone Country Office, Freetown, Sierra Leone.
authors.forename: Aychiluhim Damtew
authors.initials: AD
authors.lastname: Mitiku
authors.affiliation: Kenema District Health Management Team, Kenema District, Sierra Leone.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Vandi
authors.affiliation: Ministry of Health and Sanitation, Freetown, Sierra Leone.
authors.forename: David
authors.initials: D
authors.lastname: Kargbo
authors.affiliation: Department of Pandemic and Epidemic Diseases, World Health Organization, Geneva, Switzerland.
authors.forename: Pierre
authors.initials: P
authors.lastname: Formenty
authors.affiliation: Department of Global Capacities, Alert and Response, World Health Organization, Geneva, Switzerland.
authors.forename: Stephane
authors.initials: S
authors.lastname: Hugonnet
authors.affiliation: Department of Pandemic and Epidemic Diseases, World Health Organization, Geneva, Switzerland.
authors.forename: Eric
authors.initials: E
authors.lastname: Bertherat
authors.affiliation: Global Outbreak and Alert Response Network (GOARN), World Health Organization, Geneva, Switzerland.|Public Health England, London NW9 5EQ, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Lane
mesh_terms: D016358:Contact Tracing; D058872:Epidemics; D019142:Hemorrhagic Fever, Ebola / Q000453:epidemiology* / Q000635:transmission* / Q000821:virology; D006801:Humans; D012189:Retrospective Studies; D012807:Sierra Leone / Q000453:epidemiology
keywords: Ebola virus disease; contact tracing; haemorrhagic fever; outbreaks; surveillance