The genesis of the Ebola virus outbreak in west Africa

The 2013–16 Ebola virus outbreak in west Africa was purported to have begun in the Guinean village of Meliandou in December, 2013.1WHOOrigins of the 2014 Ebola epidemic.https://www.who.int/csr/disease/ebola/one-year-report/virus-origin/en/Date: 2015Date accessed: January 11, 2019Google Scholar Authorities recorded 11 cases of Ebola virus disease (EVD) at this “index site” (where the virus is believed to have first spilled over into the human population), with 100% case fatality. In The Lancet Infectious Diseases, Joseph WS Timothy and colleagues2Timothy JWS Hall Y Akoi-Boré J et al.Early transmission and case fatality of Ebola virus at the index site of the 2013–16 west African Ebola outbreak: a cross-sectional seroprevalence survey.Lancet Infect Dis. 2019; (published online Feb 21.)http://dx.doi.org/10.1016/S1473-3099(18)30791-6Summary Full Text Full Text PDF PubMed Scopus (11) Google Scholar present a brilliant piece of epidemiological sleuthing. By combining classic field investigations with an assay that can measure Ebola virus antibodies in oral fluid, the authors have improved our understanding of the early development of the outbreak in Meliandou. They show that there was almost double the number of individuals infected with Ebola virus (21 cases vs the 11 cases previously reported), and the case fatality was 55·6%. The non-invasive assay used in this study reportedly has high specificity,3Glynn JR Bower H Johnson S et al.Asymptomatic infection and unrecognised Ebola virus disease in Ebola-affected households in Sierra Leone: a cross-sectional study using a new non-invasive assay for antibodies to Ebola virus.Lancet Infect Dis. 2017; 17: 645-653Summary Full Text Full Text PDF PubMed Scopus (70) Google Scholar although the scarce number of negative controls (almost all UK-based), change in cutoff from previous studies, and imperfect orthogonal corroboration restricted to symptomatic participants (as opposed to those deemed minimally symptomatic) mean that further validation of the assay would be welcome. In our previous study4Richardson ET Kelly JD Barrie MB et al.Minimally symptomatic infection in an Ebola ‘hotspot’: a cross-sectional serosurvey.PLoS Negl Trop Dis. 2016; 10: e0005087Crossref PubMed Scopus (42) Google Scholar in Sierra Leone, we found—albeit with a different assay—that European and American negative controls provide much less noise and thus prompt lower optical density cutoffs (the threshold for determining whether someone is a case or not) than do controls in west Africa, potentially due to cross-reactivity of our assay with closely related pathogens circulating in the region. Timothy and colleagues corroborate emerging evidence that suggest minimally symptomatic infections were common in the 2013–16 outbreak in west Africa and that a substantial portion of Ebola transmission events might have been undetected during the outbreak.4Richardson ET Kelly JD Barrie MB et al.Minimally symptomatic infection in an Ebola ‘hotspot’: a cross-sectional serosurvey.PLoS Negl Trop Dis. 2016; 10: e0005087Crossref PubMed Scopus (42) Google Scholar, 5Kelly JD Barrie MB Mesman AW et al.Anatomy of a ‘hotspot’: a cross-sectional, seroepidemiological study of Ebola virus transmission in the village of Sukudu, Sierra Leone.J Infect Dis. 2018; 217: 1214-1221Crossref PubMed Scopus (12) Google Scholar Indeed, even WHO has admitted that the true toll of the epidemic “was certainly greater” than the 28 616 suspected, probable, and confirmed cases of EVD that were reported.6WHO Ebola Response TeamAfter Ebola in west Africa—unpredictable risks, preventable epidemics.N Engl J Med. 2016; 375: 587-596Crossref PubMed Scopus (179) Google Scholar Notwithstanding the minor limitation of recall bias, most will agree that this well designed study yields important insights into the genesis of the 2013–16 Ebola virus outbreak in west Africa; however, we must be wary of leaving epidemics to the epidemiologists. It is important to consider that the real genesis of this preventable outbreak is the combined effect of the legacies of slavery (ie, Maafa7Richardson ET Kelly JD Sesay O et al.The symbolic violence of ‘outbreak’: a mixed-methods, quasi-experimental impact evaluation of social protection on Ebola survivor wellbeing.Soc Sci Med. 2017; 195: 77-82Crossref PubMed Scopus (21) Google Scholar), exploitative colonialism, purposeful underdevelopment, structural adjustment, resource extraction, illicit financial flows, poverty, gender violence, and enabled civil war.8Richardson ET Barrie MB Kelly JD Dibba Y Koedoyoma S Farmer PE Biosocial approaches to the 2013–16 Ebola pandemic.Health Hum Rights. 2016; 18: 167-179Google Scholar, 9Fallah MP Skrip LA Gertler S Yamin D Galvani AP Quantifying poverty as a driver of Ebola transmission.PLoS Negl Trop Dis. 2016; 9: e0004260Google Scholar When viewed through this lens, even the revised case fatality of 55·6% is misleading: we estimate the true case fatality of EVD to be less than 10% when patients have access to a high-level intensive care unit—notably, all repatriated Americans infected with Ebola virus survived.10Richardson ET Barrie MB Nutt CT et al.The Ebola suspect's dilemma.Lancet Glob Health. 2017; 5: e254-e256Summary Full Text Full Text PDF PubMed Scopus (25) Google Scholar In summary, although highly skillful work—like that of Timothy and colleagues—is integral to improved understanding of viral transmission dynamics, such virtuosity should not obscure recognition of the structural determinants of epidemics.11Farmer P Infections and inequalities: the modern plagues. University of California Press, Berkeley, CA2001Google Scholar This online publication has been corrected. The corrected version first appeared at thelancet.com/infection on March 29, 2019 This online publication has been corrected. The corrected version first appeared at thelancet.com/infection on March 29, 2019 We declare no competing interests. Early transmission and case fatality of Ebola virus at the index site of the 2013–16 west African Ebola outbreak: a cross-sectional seroprevalence surveyEbola virus infection was more widespread in this spillover population than previously recognised (21 vs 11 cases). We show the first serological evidence of survivors in this population (eight anti-Ebola virus IgG seropositive) and report a case fatality lower than previously reported (55·6% vs 100% in adults). These data show the high community coverage achievable by using a non-invasive test and, by accurately documenting the beginnings of the west African Ebola virus outbreak, reveal important insight into transmission dynamics and risk factors that underpin Ebola virus spillover events. Full-Text PDF Open AccessCorrection to Lancet Infect Dis 2019; 19: 348–49Richardson ET, Fallah MP. The genesis of the Ebola virus outbreak in west Africa. Lancet Infect Dis 2019; 19: 48–49—In this Comment, the following sentence was deleted because the data are unverified and, therefore, could be unreliable: “The PREVAIL studies in Liberia are also revealing that, when longitudinally followed up, some individuals' titres switch from positive to negative and vice-versa, showing that identifying true Ebola virus infections by ELISA is not yet an exact science”. This correction has been made to the online version as of March 29, 2019. Full-Text PDF Open Access

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