Epidemiology and Risk Factors for Ebola Virus Disease in Sierra Leone-23 May 2014 to 31 January 2015

Background. Sierra Leone has the most cases of Ebola virus disease (EVD) ever reported. Trends in laboratory-confirmed EVD, symptom presentation, and risk factors have not been fully described. Methods. EVD cases occurring from 23 May 2014 to 31 January 2015 are presented by geography, demographics, and risk factors for all persons who had laboratory-confirmed EVD, which was identified by Ebola virus-specific reverse-transcription polymerase chain reaction-based testing. Results. During the study period, 8056 persons had laboratory-confirmed EVD. Their median age was 28 years; 51.7% were female. Common symptoms included fever (90.4%), fatigue (88.3%), loss of appetite (87.0%), headache (77.9%), joint pain (73.7%), vomiting (71.2%), and diarrhea (70.6%). Among persons with confirmed cases, 47.9% reported having had contact with someone with suspected EVD or any sick person, and 25.5% reported having attended a funeral, of whom 66.2% reported touching the body. The incidence of EVD was highest during 1-30 November 2014, at 7.5 per 100 000 population per week, and decreased to 2.1 per week during 1-31 January 2015. Between 23 May and 30 August 2014, two districts had the highest incidence of 3.8 and 7.0 per 100 000 population per week which decreased >97% by 1-31 January 2015. In comparison, the districts that include the capital city reported a 10-fold increase in incidence per week during the same time periods. Conclusions. Almost half of patients with EVD in Sierra Leone reported physical contact with a person ill with EVD or a dead body, highlighting prevention opportunities.