Response to Ebola Virus Disease Outbreak: Experience in Field Epidemiology in Sierra Leone

: The Ebola virus disease (EVD) outbreak that occurred in West Africa in 2014 was the largest ever in the world. In Sierra Leone, the number of cases reported peaked in December 2014 and gradually declined. However, the outbreak was not immediately terminated. To support the response of the World Health Organization (WHO) to EVD, the WHO Western Pacific Regional Office established the Western Pacific Ebola Support Team (WEST) with the aim of eliminating EVD in Port Loko District, where a certain number of new cases were still being reported in March 2015. We were dispatched to join WEST as WHO short term consultants in epidemiology for about six weeks from March to June 2015. Here, we describe our activities in the field as epidemiologists to show how Japan can contribute in the area of epidemiology during infectious disease outbreaks of international concern. The analysis suggested that the surveillance data for all the deaths and suspected EVD cases were underreporting the actual number of EVD cases in Port Loko District. Although contact tracing was conducted, new EVD cases were often found among untraced contacts because of inadequate information from residents or insufficient investigation by the contact tracing team. In addition, incomplete monitoring of the health status of close contacts resulted in secondary transmission of the disease. Data managers established a database by centralizing data from the surveillance and contact tracing teams, laboratories, and healthcare facilities. The number of deaths per week recorded by these data sources was lower than the number of deaths per week that would be expected from the national mortality statistics. The team strengthened surveillance and social mobilization in the regions with wide disparities between the actual and reported numbers of deaths. For the on-the-ground activities, the field coordinator, epidemiologists, and social mobilizers, as well as the logistic and administrative support personnel, were all indispensable in supporting the field investigation of these infectious disease outbreaks of public health concern. A field coordinator, in particular, requires outstanding knowledge, experience and skills to lead team operations in liaison with international and local partners and to build confidence among local residents. The development of these human resources and the maintenance of a response team are required for potential future outbreaks, and this is an important area that Japan could prepare for and then contribute to future outbreaks. This report does not represent an official view of the WHO or our affiliates.