Illustration by Michael S. Helfenbein/Yale University
Key Points:
- Researchers identified a single antiviral protein that can indicate the presence of stealthy unknown viruses.
- Screening for the biomarker can allow researchers to narrow down the search for unexpected pathogens.
- The method was successful when used to retest old samples to search for missed cases of COVID-19 in the early days of the pandemic.
Yale University researchers have found that testing for the presence of a single immune system molecule on nasal swabs can help detect stealthy viruses not identified in standard tests.
Public health officials typically look to a few sources for warning signs of emerging disease. In addition to studying emerging viruses in animals, researchers and doctors look for an outbreak of unexplained respiratory ailments.
Nasal swabs are commonly taken from patients with suspected respiratory infections and are tested to detect specific signatures of 10 to 15 known viruses. Most tests come back negative.
But, in 2017, Ellen Foxman, associate professor of laboratory medicine and immunobiology, noticed that in a few cases the swabs of those who tested negative for the “usual suspect” viruses still exhibited signs that antiviral defenses were activated, indicating the presence of a virus. The telltale sign was a high level of a single antiviral protein made by the cells that line the nasal passages.
Based on that finding, in the newest study published in Lancet Microbe, Foxman and her team applied comprehensive genetic sequencing methods to old samples containing the protein and, in one sample, found an unexpected influenza virus, called influenza C.
They also retested old samples to search for missed cases of COVID-19 during the first two weeks of March 2020. Hundreds of nasal swab samples collected from patients at Yale-New Haven Hospital during that time had tested negative for standard signature viruses. When tested for the immune system biomarker, the vast majority of those samples showed no trace of activity of the antiviral defense system. But a few did; among those, the team found four cases of COVID-19 that had gone undiagnosed at the time.
The findings reveal that testing for an antiviral protein made by the body, even if the tests for known respiratory viruses are negative, can help pinpoint which nasal swabs are more likely to contain unexpected viruses.
Specifically, screening for the biomarker can allow researchers to narrow down the search for unexpected pathogens, making it feasible to do surveillance for unexpected viruses using swabs collected during routine patient care.
Information provided by Yale University.