Evaluation of Ebola virus disease surveillance system in Tonkolili District, Sierra Leone

The Ebola Virus Disease (EVD) epidemic devastated West Africa, with Sierra Leone recording over 50% of the 28,610 cases across the three most affected countries. Enhanced surveillance system was developed for improved identification of cases and response in Sierra Leone. Here, we evaluated the surveillance system to determine its strengths and challenges in meeting the set objectives.

The EVD surveillance system in Tonkolili District, Sierra Leone, was assessed using the CDC updated guidelines for evaluating public health surveillance. In particular, the simplicity, stability, acceptability, flexibility, representativeness, sensitivity, positive predictive value and data quality of the system were assessed using EVD surveillance data and information from key informant interviews with program stakeholders.

The EVD surveillance system in Tonkolili District provided information and data on disease trends and outbreak report through official and rumours sources. Case definitions were well understood by participants, with willingness to continue surveillance activities after the EVD outbreak. Standardized data collection tools were in place and data communication was clear with feedback to surveillance units at all levels. The EVD surveillance was not operated within the Integrated Disease Surveillance and Response framework (IDSR). Data completeness was about 91%, consistency existed but data quality was poor (incompletely filled data and missing data existed). Regarding timeliness, samples arrived designated laboratory within 24 - 48 hours in 174 (84.9%). Sensitivity of the surveillance system was 88.5%. Predictive value positive was 25.8%. The stability was questionable since the government of Sierra Leone were not fully in charge of the system.

While the simplicity of the EVD surveillance system in Tonkolili District facilitated its implementation, users suggested that the system did not meet expectations in terms of timeliness, flexibility and acceptability. There was a need to channel efforts towards integrating EVD surveillance into the IDSR. Data completeness and timeliness needed more attention. The District Health Management Team need to take ownership of the surveillance system for sustainability.