Interviews with the individuals revealed that whereas two of the seropositive individuals did report a fever during quarantine, the remaining 12 did not recall having any symptoms consistent with EVD.
"Although it was difficult to verify symptoms through our retrospective interviews (given the considerable denial of EVD during the outbreak due to stigma and the fear of being admitted to an [Ebola treatment unit,] where those admitted were seldom discharged), our data indicate that 25% of EBOV infections may have been minimally symptomatic, which is similar to the data from empiric studies and to recent modeled estimates," the authors write.
Dr Richardson and colleagues note that when EBOV was discovered in 1976, scientists noted that infection could result in minimal symptoms. The new results provide evidence that during an outbreak, EBOV infection does, indeed, present with a full spectrum of clinical manifestations.
The data also indicate that during the outbreak, many EBOV transmission events went undetected. As a consequence, further studies are needed to understand the risk for transmission and clinical sequelae in these individuals with newly recognized EBOV infection.
"Our study focused on the quarantined population of one village," cautioned the authors. "Extrapolation of our findings to other villages and generalizability to the epidemic should be approached with caution. Although many of the study participants were followed by surveillance teams during the time of active EBOV transmission in their village, the timing of the possible infection cannot be known from [immunoglobulin G] data, and it is improbable that surveillance teams followed each individual throughout the duration of the outbreak in Sierra Leone."
