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Rapid evaluation of the effectiveness of a community event-based surveillance system for Ebola virus disease in Sierra Leone
Amidst continued transmission of Ebola virus disease (EVD) in Sierra Leone, the International Rescue Committee designed a community event-based surveillance (CEBS) system in Bo District in October 2014. CEBS aims to detect unknown chains of transmission through trigger events at the village level which provide early warning of community deaths, illness clusters and unsafe burials. Based on the results, the Ebola Response Consortium (ERC) and the MoHS scaled up CEBS nationally by training 7,000 community monitors to detect events in nine of the 14 districts. In May 2015, we evaluated the system’s capacity to detect alerts and the completeness and timeliness of confirmed case detection.
Methods
We conducted descriptive analyses of alerts and responses in eight districts from February 19 to June 15, 2015. To analyze the effectiveness of confirmed case detection, we compared the number of cases detected through CEBS and surveillance statistics over one month. For confirmed cases from unknown chains of transmission, we compared the delay between the date of symptom onset and date of reporting for cases detected and undetected by CEBS.
Results
CEBS generated 3,432 alerts over the time period. 2,932 (85%) community deaths, 480 (14%) illness clusters and six unsafe burials were reported. 2,784 (88%) alerts were escalated and responded to. 131 (5%) met the suspect or probable case definition and tested negative. CEBS was involved in detecting seven of the 12 (58%) confirmed cases in Kambia district, the only supported district with transmission. CEBS detected three of the five (60%) confirmed cases that originated from unknown chains of transmission. For these cases, the delay between date of symptom onset and reporting was two to three days if identified by CEBS and five to seven days if identified by another source. CEBS found three measles outbreaks.
Discussion
CEBS provided sensitive and timely detection of cases from unknown chains of transmission. By ruling out suspect cases, it confirmed zero transmission in quiet districts. It provided substantial levels of community death and measles reporting. Maintaining vigilance and timeliness of reporting after the emergency will be a challenge to its sustainability and expansion to other diseases.
Learning Areas:
Conduct evaluation related to programs, research, and other areas of practiceEpidemiology
Protection of the public in relation to communicable diseases including prevention or control
Public health or related research
Learning Objectives:
Demonstrate the functioning of a novel surveillance system setup during an emergency (the 2014-present Ebola virus disease outbreak)
Demonstrate the process of rapidly evaluating a surveillance system
Keyword(s): Surveillance, International Health
Qualified on the content I am responsible for because: I am an epidemiologist who works on the evaluation of health programs and control of infectious diseases for the International Rescue Committee. I contributed to the design, data collection, analysis and reporting for this evaluation.
Any relevant financial relationships? No
I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.