Surveillance in the field: Over-identification of Ebola suspect cases and its contributing factors in West African at-risk contexts

Clinical and epidemiological performance of WHO Ebola case definitions: a systematic review and meta-analysis

BACKGROUND

Ebola virus disease case definition is a crucial surveillance tool to detect suspected cases for referral and as a screening tool for clinicians to support admission and laboratory testing decisions at Ebola health facilities. We aimed to assess the performance of the WHO Ebola virus disease case definitions and other screening scores.

METHODS

In this systematic review and meta-analysis, we searched PubMed, Scopus, Embase, and Web of Science for studies published in English between June 13, 1978, and Jan 14, 2020. We included studies that estimated the sensitivity and specificity of WHO Ebola virus disease case definitions, clinical and epidemiological characteristics (symptoms at admission and contact history), and predictive risk scores against the reference standard (laboratory-confirmed Ebola virus disease). Summary estimates of sensitivity and specificity were calculated using bivariate and hierarchical summary receiver operating characteristic (when four or more studies provided data) or random-effects meta-analysis (fewer than four studies provided data).

FINDINGS

We identified 2493 publications, of which 14 studies from four countries (Sierra Leone, Guinea, Liberia, and Angola) were included in the analysis. 12 021 people with suspected disease were included, of whom 4874 were confirmed as positive for Ebola virus infection. Six studies explored the performance of WHO case definitions in non-paediatric populations, and in all of these studies, suspected and probable cases were combined and could not be disaggregated for analysis. The pooled sensitivity of the WHO Ebola virus disease case definitions from these studies was 81·5% (95% CI 74·1-87·2) and pooled specificity was 35·7% (28·5-43·6). History of contact or epidemiological link was a key predictor for the WHO case definitions (seven studies) and for risk scores (six studies). The most sensitive symptom was intense fatigue (79·0% [95% CI 74·4-83·0]), assessed in seven studies, and the least sensitive symptom was pain behind the eyes (1·0% [0·0-7·0]), assessed in three studies. The performance of fever as a symptom varied depending on the cutoff used to define fever.

INTERPRETATION

WHO Ebola virus disease case definitions perform suboptimally to identify cases at both community level and during triage at Ebola health facilities. Inclusion of intense fatigue as a key symptom and contact history could improve the performance of case definitions, but implementation of these changes will require effective collaboration with, and trust of, affected communities.

FUNDING

Médecins sans Frontières.

[Neglected patients, unexpected effects. Ebola virus disease suspected case experience.]

INTRODUCTION

In an epidemic context, the identification of suspected cases, among alert or contact cases, leads to caring for persons for whom only a minority will be confirmed cases, with a laboratory diagnosis positive for Ebola. How are suspected cases treated that are not subsequently confirmed and how do they feel about this experience ? What are the medical or social consequences ?

METHODS

A qualitative study was conducted in two countries with a high Ebola risk epidemic situation in 2015-2016 (Senegal, Côte d'Ivoire). Based on interviews with suspected cases and caregivers, 12 referral itineraries were identified for 20 people.

RESULTS

Narratives are dominated by the perception of failures at several levels: insufficient means and service preparation; lack of care for patients' vital needs and lack of treatment for their diseases; lack of listening, explanation and consideration for their families; patients' suffering from being isolated and facing violence; unexpected secondary social effects. These findings can be explained partly by caregivers' focus on Ebola diagnosis more than patients, fear of contagion, and by the insufficient preparation of isolation spaces at the time of the survey.

CONCLUSION

The results show the possible pitfalls of surveillance systems which increase the number of persons identified as suspected cases, if care services are not sufficiently prepared. Recommendations based on these results should be considered particularly to define operational procedures and trainings for health professionals.