Early detection of virus by nasal swab is possible: Research

The 4th of January, New York [US]: Potentially dangerous new viruses can spread across the population long before the system for tracking global public health is able to catch them, as the Covid-19 pandemic showed.
But Yale researchers have found that testing nasal swabs for a specific immune system component can assist in identifying covert viruses that are overlooked by traditional diagnostics, they report on January 3 in the journal Lancet Microbe.

“Finding a dangerous new virus is like searching for a needle in a haystack,” said Ellen Foxman, associate professor of laboratory medicine and immunobiology and senior author of the study, adding, “We found a way to significantly reduce the size of the haystack.”

Public health experts often consult a small number of sources when searching for early illness warning signals. They research new animal viruses that have the potential to infect humans. However, it might be challenging to identify which of the hundreds or thousands of new viral variations actually pose a threat. Additionally, they search for cases of unexplained respiratory illness outbreaks, which is how SARS-Cov-2, the virus that causes Covid-19, was found in China late in 2019.
But it could be too late to stop the spread of a new virus by the time an outbreak happens.

For the current study, Foxman and her team went back to an observation they had made in their lab in 2017, which they believed would offer a fresh method for keeping an eye out for unforeseen infections. Patients with suspected respiratory infections frequently have nasal swabs obtained, which are then examined to look for particular signs of 10 to 15 recognised viruses. Most testing yield negative results.

The swabs of a few individuals who tested negative for the “usual suspect” viruses, however, nonetheless showed signals that antiviral defences were active, indicating the existence of a virus, as Foxman’s team noticed in 2017. A significant concentration of a specific antiviral protein produced by the cells lining the nasal passages served as the warning indicator.
Based on that discovery, the researchers used thorough genetic sequencing techniques to previous samples that contained the protein and discovered an unexpected influenza virus, known as influenza C, in one sample.
During the first two weeks of March 2020, the researchers employed the same method of retesting previous samples to look for missing instances of Covid-19.

Although the virus had started to cause instances in New York State at around the same time, testing was not accessible until several weeks later. Numerous nasal swab samples taken during that period from patients at Yale-New Haven Hospital had tested negative for common characteristic viruses. The great majority of those samples revealed no evidence of antiviral defence system activation when examined for immune system biomarkers. But a handful did, and among them, the investigators discovered four cases of Covid-19 that had previously gone untreated. The results show that testing for an antiviral protein produced by the body can help identify which nasal swabs are more likely to contain unexpected viruses, even if tests for recognised respiratory viruses are negative.

Researchers may be able to focus their search for unexpected infections by screening for the biomarker, which makes it possible to conduct monitoring for unexpected viruses using swabs obtained during standard patient treatment. In order to uncover unexpected or emergent infections circulating in the patient population and to prompt a reaction from the medical community, samples found to have the biomarker can be evaluated using more sophisticated genetic testing techniques.