Evaluation of a National Call Center and a Local Alerts System for Detection of New Cases of Ebola Virus Disease — Guinea, 2014–2015

Abstract

The epidemic of Ebola virus disease (Ebola) in West Africa began in Guinea in late 2013 (1), and on August 8, 2014, the World Health Organization (WHO) declared the epidemic a Public Health Emergency of International Concern (2). Guinea was declared Ebola-free on December 29, 2015, and is under a 90 day period of enhanced surveillance, following 3,351 confirmed and 453 probable cases of Ebola and 2,536 deaths (3). Passive surveillance for Ebola in Guinea has been conducted principally through the use of a telephone alert system. Community members and health facilities report deaths and suspected Ebola cases to local alert numbers operated by prefecture health departments or to a national toll-free call center. The national call center additionally functions as a source of public health information by responding to questions from the public about Ebola. To evaluate the sensitivity of the two systems and compare the sensitivity of the national call center with the local alerts system, the CDC country team performed probabilistic record linkage of the combined prefecture alerts database, as well as the national call center database, with the national viral hemorrhagic fever (VHF) database; the VHF database contains records of all known confirmed Ebola cases. Among 17,309 alert calls analyzed from the national call center, 71 were linked to 1,838 confirmed Ebola cases in the VHF database, yielding a sensitivity of 3.9%. The sensitivity of the national call center was highest in the capital city of Conakry (11.4%) and lower in other prefectures. In comparison, the local alerts system had a sensitivity of 51.1%. Local public health infrastructure plays an important role in surveillance in an epidemic setting.

Event-based surveillance at health facility and community level in low-income and middle-income countries: a systematic review

“…The 17 identified records referred to 15 studies (based on individual sets of data) and 13 different EBS systems 8–24. For the quality appraisal, we assessed each of the 15 studies.…”

“…We identified three EBS systems that were ‘open’ to receive outbreak-specific event notifications from anyone: the telephone hotlines during the Ebola outbreak in Guinea18 and Sierra Leone21 allowed anyone to notify unspecified Ebola-related events; signals received by call centres were forwarded to the Ebola response structure in place for verification and response 18 21. Similarly, the EBS system in place in Haiti at the start of the cholera outbreak allowed partners within and outside the UN health cluster to notify an additional list of defined cholera-related events, including the lack of access to healthcare and sanitation 25.…”

“…Open Ebola telephone hotlines during the Ebola outbreak in Sierra Leone and Guinea received signals for cases: during a 3-day campaign in Sierra Leone, 75% of calls were verified as alerts,21 while only 12% of calls were verified as alerts over 10 months in Guinea 18. Alerts were investigated by the response teams in place though the number of true events (identified case(s) meeting the case definition) was not reported.…”

“…In outbreak context, Ratnayake et al 19 reported that 30% (16/53) of all confirmed cases of Ebola in the area where CEBS for Ebola was implemented were identified by CEBS. In Guinea, 3.9% (71/1838) of all confirmed Ebola cases were identified by signals received at the national Ebola call centre and 54% (120/221) of all confirmed Ebola cases were identified by local Ebola alert numbers18 (online supplementary file 4).…”

“…For CEBS in outbreak settings, specified event definitions that indicate disease transmission had low specificity and event definitions were not always remembered long after trainings,17 19 20 suggesting that definitions should be more rigorously tested prior to implementation 19. Telephone hotlines were mostly used for information by the public (and useful for improving communication with the public) but also identified cases that went under the radar of IBS18 and from areas outside the reach of IBS 25. EBS in communities showed a higher specificity than EBS using open hotlines, at the costs of limited reach (limited to communities with CEBS vs anywhere with phone connection) 18 19.…”