Association of Lower Exposure Risk With Paucisymptomatic/Asymptomatic Infection, Less Severe Disease, and Unrecognized Ebola Virus Disease: A Seroepidemiological Study

J Daniel Kelly; Raphael G Frankfurter; Jacqueline M Tavs; Mohamed Bailor Barrie; Timothy McGinnis; Mohamed Kamara; Adams Freeman; Komba Quiwah; Michelle C Davidson; Bonnie Dighero-Kemp; Harrison Gichini; Elizabeth Elliott; Cavan Reilly; Lisa E Hensley; H Clifford Lane; Sheri D Weiser; Travis C Porco; George W Rutherford; Eugene T Richardson

doi:10.1093/ofid/ofac052

Association of Lower Exposure Risk With Paucisymptomatic/Asymptomatic Infection, Less Severe Disease, and Unrecognized Ebola Virus Disease: A Seroepidemiological Study

Open Forum Infect Dis. 2022 Mar 7;9(4):ofac052. doi: 10.1093/ofid/ofac052. eCollection 2022 Apr.

Authors

J Daniel Kelly^{1

2

3

4}, Raphael G Frankfurter⁵, Jacqueline M Tavs³, Mohamed Bailor Barrie^{1

2

4}, Timothy McGinnis⁶, Mohamed Kamara⁴, Adams Freeman⁴, Komba Quiwah⁴, Michelle C Davidson⁵, Bonnie Dighero-Kemp⁷, Harrison Gichini⁷, Elizabeth Elliott⁷, Cavan Reilly⁸, Lisa E Hensley⁷, H Clifford Lane⁷, Sheri D Weiser⁹, Travis C Porco^{1

3}, George W Rutherford^{1

2}, Eugene T Richardson^{4

6

10}

Affiliations

¹ Department of Epidemiology and Biostatistics, University of California, San Francisco, California, USA.
² Institute for Global Health Sciences, University of California, San Francisco, California, USA.
³ F. I. Proctor Foundation, University of California, San Francisco, California, USA.
⁴ Partners In Health, Freetown, Sierra Leone.
⁵ School of Medicine, University of California, San Francisco, California, USA.
⁶ Department of Global Health and Social Medicine, Harvard Medical School, Boston, Massachusetts, USA.
⁷ Integrated Research Facility, National Institute of Allergy and Infectious Diseases, Fort Detrick, Maryland, USA.
⁸ Division of Biostatistics, University of Minnesota, Minneapolis, Minnesota, USA.
⁹ Division of HIV, Infectious Disease, and Global Medicine, Department of Medicine, University of California, San Francisco, San Francisco, California, USA.
¹⁰ Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA.

Abstract

Background: It remains unclear if there is a dose-dependent relationship between exposure risk to Ebola virus (EBOV) and severity of illness.

Methods: From September 2016 to July 2017, we conducted a cross-sectional, community-based study of Ebola virus disease (EVD) cases and household contacts of several transmission chains in Kono District, Sierra Leone. We analyzed 154 quarantined households, comprising both reported EVD cases and their close contacts. We used epidemiological surveys and blood samples to define severity of illness as no infection, pauci-/asymptomatic infection, unrecognized EVD, reported EVD cases who survived, or reported EVD decedents. We determine seropositivity with the Filovirus Animal Nonclinical Group EBOV glycoprotein immunoglobulin G antibody test. We defined levels of exposure risk from 8 questions and considered contact with body fluid as maximum exposure risk.

Results: Our analysis included 76 reported EVD cases (both decedents and survivors) and 421 close contacts. Among these contacts, 40 were seropositive (22 paucisymptomatic and 18 unrecognized EVD), accounting for 34% of the total 116 EBOV infections. Higher exposure risks were associated with having had EBOV infection (maximum risk: adjusted odds ratio [AOR], 12.1 [95% confidence interval {CI}, 5.8-25.4; trend test: P < .001) and more severe illness (maximum risk: AOR, 25.2 [95% CI, 6.2-102.4]; trend test: P < .001).

Conclusions: This community-based study of EVD cases and contacts provides epidemiological evidence of a dose-dependent relationship between exposure risk and severity of illness, which may partially explain why pauci-/asymptomatic EBOV infection, less severe disease, and unrecognized EVD occurs.

Keywords: Ebola virus; epidemiology; exposure risk; public health; transmission.

Abstract

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