Ebola exposure, illness experience, and Ebola antibody prevalence in international responders to the West African Ebola epidemic 2014–2016: A cross-sectional study

Catherine F. Houlihan*, Catherine R. McGowan, Steve Dicks, Marc Baguelin, David A.J. Moore, David Mabey, Chrissy h. Roberts, Alex Kumar, Richard Tedder, Judith R. Glynn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

Background: Healthcare and other front-line workers are at particular risk of infection with Ebola virus (EBOV). Despite the large-scale deployment of international responders, few cases of Ebola virus disease have been diagnosed in this group. Since asymptomatic or pauci-symptomatic infection has been described, it is plausible that infections have occurred in healthcare workers but have escaped being diagnosed. We aimed to assess the prevalence of asymptomatic or pauci-symptomatic infection, and of exposure events, among returned responders to the West African Ebola epidemic 2014–2016. Methods and findings: We used snowball sampling to identify responders who had returned to the UK or Ireland, and used an online consent and questionnaire to determine their exposure to EBOV and their experience of illness. Oral fluid collection devices were sent and returned by post, and samples were tested using an EBOV IgG capture assay that detects IgG to Ebola glycoprotein. Blood was collected from returnees with reactive samples for further testing. Unexposed UK controls were also recruited. In all, 300 individuals consented, of whom 268 (89.3%) returned an oral fluid sample (OFS). The majority had worked in Sierra Leone in clinical, laboratory, research, and other roles. Fifty-three UK controls consented and provided samples using the same method. Of the returnees, 47 (17.5%) reported that they had had a possible EBOV exposure. Based on their free-text descriptions, using a published risk assessment method, we classified 43 (16%) as having had incidents with risk of Ebola transmission, including five intermediate-risk and one high-risk exposure. Of the returnees, 57 (21%) reported a febrile or diarrhoeal illness in West Africa or within 1 mo of return, of whom 40 (70%) were not tested at the time for EBOV infection. Of the 268 OFSs, 266 were unreactive. Two returnees, who did not experience an illness in West Africa or on return, had OFSs that were reactive on the EBOV IgG capture assay, with similar results on plasma. One individual had no further positive test results; the other had a positive result on a double-antigen bridging assay but not on a competitive assay or on an indirect EBOV IgG ELISA. All 53 controls had non-reactive OFSs. While the participants were not a random sample of returnees, the number participating was high. Conclusions: This is the first study, to our knowledge, of the prevalence of EBOV infection in international responders. More than 99% had clear negative results. Sera from two individuals had discordant results on the different assays; both were negative on the competitive assay, suggesting that prior infection was unlikely. The finding that a significant proportion experienced “near miss” exposure events, and that most of those who experienced symptoms did not get tested for EBOV at the time, suggests a need to review and standardise protocols for the management of possible exposure to EBOV, and for the management of illness, across organisations that deploy staff to outbreaks.

Original languageEnglish
Article numbere1002300
JournalPLoS Medicine
Volume14
Issue number5
DOIs
Publication statusPublished - May 2017

Bibliographical note

Funding Information:
CFH and JRG received funding from the Wellcome Trust: Enhancing Research Activity in Epidemic Situations, grant number WT-106491/Z/14/Z. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors would like to thank LSHTM and PHE for providing laboratory services to support this study. We would also like to thank the Multimedia Department at LSHTM for helping to create our self-test materials. We are very grateful to Anne Koerber, Kes Stern, Magda Bondos, Dr. Colin Brown, and Dr. Landon Kuester for their assistance with this study. Additional thanks are owed to Professor Dame Anne Mills for assistance with recruitment. Finally, we are grateful to Dr. Katie Ewer and Georgina Bowyer at the Jenner Institute, University of Oxford, for testing the reactive samples from two returnees and providing advice on interpretation.

Publisher Copyright:
© 2017 Houlihan et al.

Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.

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