Publications

INTRODUCTION

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.'

METHODOLOGY/PRINCIPAL FINDINGS

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.

CONCLUSIONS/SIGNIFICANCE

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.

The American Thoracic Society celebrates the 50th anniversary of the National Institute of Environmental Health Sciences (NIEHS). The NIEHS has had enormous impact through its focus on research, training, and translational science on lung health. It has been an advocate for clean air both in the United States and across the world. The cutting-edge science funded by the NIEHS has led to major discoveries that have broadened our understanding of the pathogenesis and treatment for lung disease. Importantly, the NIEHS has developed and fostered mechanisms that require cross-cutting science across the spectrum of areas of inquiry, bringing together environmental and social scientists with clinicians to bring their expertise on specific areas of investigation. The intramural program of the NIEHS nurtures cutting-edge science, and the extramural program encourages investigator-initiated research while at the same time providing broader direction through important initiatives. Under the umbrella of the NIEHS and guided by Dr. Linda Birnbaum, the director of the NIEHS, important collaborative programs, such as the Superfund Program and the National Toxicology Program, work to discover mechanisms to protect from environmental toxins. The American Thoracic Society has overlapping goals with the NIEHS, and the strategic plans of both august bodies converge to synergize on population lung health. These bonds must be tightened and highlighted as we work toward our common goals.