title: Minimally Symptomatic Infection in an Ebola 'Hotspot': A Cross-Sectional Serosurvey.
abstract: Evidence for minimally symptomatic Ebola virus (EBOV) infection is limited. During the 2013-16 outbreak in West Africa, it was not considered epidemiologically relevant to published models or projections of intervention effects. In order to improve our understanding of the transmission dynamics of EBOV in humans, we investigated the occurrence of minimally symptomatic EBOV infection in quarantined contacts of reported Ebola virus disease cases in a recognized 'hotspot.'
  
  
  
  We conducted a cross-sectional serosurvey in Sukudu, Kono District, Sierra Leone, from October 2015 to January 2016. A blood sample was collected from 187 study participants, 132 negative controls (individuals with a low likelihood of previous exposure to Ebola virus), and 30 positive controls (Ebola virus disease survivors). IgG responses to Ebola glycoprotein and nucleoprotein were measured using Alpha Diagnostic International ELISA kits with plasma diluted at 1:200. Optical density was read at 450 nm (subtracting OD at 630nm to normalize well background) on a ChroMate 4300 microplate reader. A cutoff of 4.7 U/mL for the anti-GP ELISA yielded 96.7% sensitivity and 97.7% specificity in distinguishing positive and negative controls. We identified 14 seropositive individuals not known to have had Ebola virus disease. Two of the 14 seropositive individuals reported only fever during quarantine while the remaining 12 denied any signs or symptoms during quarantine.
  
  
  
  By using ELISA to measure Zaire Ebola virus antibody concentrations, we identified a significant number of individuals with previously undetected EBOV infection in a 'hotspot' village in Sierra Leone, approximately one year after the village outbreak. The findings provide further evidence that Ebola, like many other viral infections, presents with a spectrum of clinical manifestations, including minimally symptomatic infection. These data also suggest that a significant portion of Ebola transmission events may have gone undetected during the outbreak. Further studies are needed to understand the potential risk of transmission and clinical sequelae in individuals with previously undetected EBOV infection.
authors.affiliation: Department of Anthropology, Stanford University, Stanford, United States of America.|Division of Global Health Equity, Brigham and Women's Hospital, Boston, United States of America.|Partners In Health, Sierra Leone.
authors.forename: Eugene T
authors.identifier: 0000-0001-8437-0671
authors.initials: ET
authors.lastname: Richardson
authors.affiliation: Partners In Health, Sierra Leone.|UCSF School of Medicine, San Francisco, United States of America.
authors.forename: J Daniel
authors.initials: JD
authors.lastname: Kelly
authors.affiliation: Partners In Health, Sierra Leone.|Department of Global Health and Social Medicine, Harvard Medical School, Boston, United States of America.
authors.forename: Mohamed Bailor
authors.initials: MB
authors.lastname: Barrie
authors.affiliation: Partners In Health, Sierra Leone.
authors.forename: Annelies W
authors.initials: AW
authors.lastname: Mesman
authors.affiliation: Partners In Health, Sierra Leone.
authors.forename: Sahr
authors.initials: S
authors.lastname: Karku
authors.affiliation: Partners In Health, Sierra Leone.
authors.forename: Komba
authors.initials: K
authors.lastname: Quiwa
authors.affiliation: Division of Global Health Equity, Brigham and Women's Hospital, Boston, United States of America.|Partners In Health, Sierra Leone.|Department of Global Health and Social Medicine, Harvard Medical School, Boston, United States of America.
authors.forename: Regan H
authors.initials: RH
authors.lastname: Marsh
authors.affiliation: Kono District Ebola Response Centre (DERC), Koidu, Sierra Leone.
authors.forename: Songor
authors.initials: S
authors.lastname: Koedoyoma
authors.affiliation: Partners In Health, Sierra Leone.
authors.forename: Fodei
authors.initials: F
authors.lastname: Daboh
authors.affiliation: Partners In Health, Sierra Leone.
authors.forename: Kathryn P
authors.initials: KP
authors.lastname: Barron
authors.affiliation: Partners In Health, Sierra Leone.
authors.forename: Michael
authors.initials: M
authors.lastname: Grady
authors.affiliation: Kono District Health Management Team (DHMT), Koidu, Sierra Leone.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Tucker
authors.affiliation: Division of Global Health Equity, Brigham and Women's Hospital, Boston, United States of America.|Partners In Health, Sierra Leone.
authors.forename: Kerry L
authors.initials: KL
authors.lastname: Dierberg
authors.affiliation: UCSF Global Health Sciences, San Francisco, United States of America.
authors.forename: George W
authors.initials: GW
authors.lastname: Rutherford
authors.affiliation: Stanford University School of Medicine, Stanford, United States of America.
authors.forename: Michele
authors.initials: M
authors.lastname: Barry
authors.affiliation: Department of Anthropology, Stanford University, Stanford, United States of America.
authors.forename: James Holland
authors.initials: JH
authors.lastname: Jones
authors.affiliation: Division of Global Health Equity, Brigham and Women's Hospital, Boston, United States of America.|Department of Global Health and Social Medicine, Harvard Medical School, Boston, United States of America.
authors.forename: Megan B
authors.initials: MB
authors.lastname: Murray
authors.affiliation: Division of Global Health Equity, Brigham and Women's Hospital, Boston, United States of America.|Partners In Health, Sierra Leone.|Department of Global Health and Social Medicine, Harvard Medical School, Boston, United States of America.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Farmer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood*; D002648:Child; D003430:Cross-Sectional Studies; D029043:Ebolavirus / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D004797:Enzyme-Linked Immunosorbent Assay; D019142:Hemorrhagic Fever, Ebola / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology; D006801:Humans; D008875:Middle Aged; D012807:Sierra Leone / Q000453:epidemiology; D014764:Viral Proteins / Q000276:immunology; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D014764:Viral Proteins