title: Epidemiology of Ebola Virus Disease in the Western Area Region of Sierra Leone, 2014-2015.
abstract: BACKGROUND
  Western Area (WA) of Sierra Leone including the capital, Freetown, experienced an unprecedented outbreak of Ebola from 2014 to 2015. At the onset of the epidemic, there was little information about the epidemiology, transmission dynamics, and risk factors in urban settings as previous outbreaks were limited to rural/semi-rural settings. This study, therefore, aimed to describe the epidemiology of the outbreak and the factors which had most impact on the transmission of the epidemic and whether there were different drivers from those previously described in rural settings.
  
  
  METHODS
  We conducted a descriptive epidemiology study in WA, Sierra Leone using secondary data from the National Ebola outbreak database. We also reviewed the Ebola situation reports, response strategy documents, and other useful documents.
  
  
  RESULTS
  A total of 4,955 Ebola cases were identified between June 2014 and November 2015, although there were reports of cases occurring in WA toward end of May. All wards were affected, and Waterloo Area I (Ward 330), the capital city of Western Area Rural District, recorded the highest numbers of cases (580) and deaths (236). Majority of cases (63.4%) and deaths (66.8%) were in WA Urban District (WAU); 44 cases were imported from other provinces. Only 20% of cases had a history of contact with an Ebola case, and more than 30% were death alerts. Equal numbers of males and females were infected, and very few cases (3.2%) were health workers. Overall, transmission was through contact with infected individuals, and intense transmission occurred at the community level. In WAU, transmission was mostly between neighbors and among inhabitants of shared accommodations. The drivers of transmission included high population movement to and from WA, overcrowding, fear and lack of trust in the response, and negative community behaviors. Transmission was mostly through contact and with limited transmission through sex and breast milk.
  
  
  CONCLUSIONS
  The unprecedented outbreak in WA was attributed to delayed detection, inadequate preparedness and response, intense population movements, overcrowding, and unresponsive communities. Anticipation, strengthening preparedness for early detection, and swift and effective response remains critical in mitigating a potential urban explosion of similar future outbreaks.
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Margaret
authors.initials: M
authors.lastname: Lamunu
authors.affiliation: World Health Organization (WHO) Country Office , Kigali , Rwanda.
authors.forename: Olushayo Oluseun
authors.initials: OO
authors.lastname: Olu
authors.affiliation: Ministry of Health and Sanitation , Freetown , Sierra Leone.
authors.forename: James
authors.initials: J
authors.lastname: Bangura
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Zabulon
authors.initials: Z
authors.lastname: Yoti
authors.affiliation: Ministry of Health and Sanitation , Freetown , Sierra Leone.
authors.forename: Thomas Takpau
authors.initials: TT
authors.lastname: Samba
authors.affiliation: Ministry of Health and Sanitation , Freetown , Sierra Leone.
authors.forename: David Kabba
authors.initials: DK
authors.lastname: Kargbo
authors.affiliation: Ministry of Health and Sanitation , Freetown , Sierra Leone.
authors.forename: Foday Mohamed
authors.initials: FM
authors.lastname: Dafae
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Muhammad Ali
authors.initials: MA
authors.lastname: Raja
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Noah
authors.initials: N
authors.lastname: Sempira
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Michael Lyazi
authors.initials: ML
authors.lastname: Ivan
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Aarti
authors.initials: A
authors.lastname: Sing
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Fredson
authors.initials: F
authors.lastname: Kurti-George
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Negusu
authors.initials: N
authors.lastname: Worku
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Pamela
authors.initials: P
authors.lastname: Mitula
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Louisa
authors.initials: L
authors.lastname: Ganda
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Robert
authors.initials: R
authors.lastname: Samupindi
authors.affiliation: Ministry of Health and Sanitation , Freetown , Sierra Leone.
authors.forename: Roland
authors.initials: R
authors.lastname: Conteh
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Kande-Bure
authors.initials: KB
authors.lastname: Kamara
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Muraguri
authors.affiliation: Ministry of Health and Sanitation , Freetown , Sierra Leone.
authors.forename: Michael
authors.initials: M
authors.lastname: Kposowa
authors.affiliation: Ministry of Health and Sanitation , Freetown , Sierra Leone.
authors.forename: Joseph
authors.initials: J
authors.lastname: Charles
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Malimbo
authors.initials: M
authors.lastname: Mugaga
authors.affiliation: World Health Organization (WHO) Headquarters , Geneva , Switzerland.
authors.forename: Christopher
authors.initials: C
authors.lastname: Dye
authors.affiliation: World Health Organization (WHO) Country Office , Freetown , Sierra Leone.
authors.forename: Anshu
authors.initials: A
authors.lastname: Banerjee
authors.affiliation: World Health Organization (WHO) Headquarters , Geneva , Switzerland.
authors.forename: Pierre
authors.initials: P
authors.lastname: Formenty
authors.affiliation: Ministry of Health and Sanitation , Freetown , Sierra Leone.
authors.forename: Brima
authors.initials: B
authors.lastname: Kargbo
authors.affiliation: World Health Organization (WHO) Headquarters , Geneva , Switzerland.
authors.forename: Raymond Bruce
authors.initials: RB
authors.lastname: Aylward
keywords: Ebola virus disease; Sierra Leone; Western Area districts; epidemiology; outbreak; risk factors; urban setting