Tests for COVID-19 usually use samples collected from the upper respiratory tract by saliva or nasopharyngeal swab. Positive samples contain active virus, but viral load in the upper respiratory tract is not correlated with symptoms in the lower respiratory tract, such as pneumonia.

“Involvement of the lower respiratory tract is often a precursor to severe COVID-19, so there is an argument for a more direct sampling focused on exhaled breath,” Fairbrother said.

Virus detection by the Bubbler is similar to a hospital-swab PCR test. However, because swab tests detect viral RNA fragments in cells that persist in previously infected cells, PCR tests can return a positive result for months after infection. By contrast, the Bubbler detects airborne viral particles and is a better measure of risk of contagion, the authors said. It can also be adapted for environmental sampling in hospitals, transportation hubs and closed environments like offices, ships and planes, the investigators wrote in the study.

“Another advantage of the Bubbler is the barcoding, which enables high-throughput RNA virus testing at a fraction of the cost of conventional testing,” Fairbrother said.

The barcode returns a viral sequence that also supports strain identification, he said, which may prove useful as more information is learned about transmissibility and possible strain-specific treatment decisions. It can also be used for simultaneous batches of pooled samples, provides additional information such as viral load and strain identity, and eliminates the need for stabilizing a sample, potentially allowing the assay to be performed at home.

The investigators also demonstrated how the Bubbler might be adapted to detect virus in airborne samples. To model the movement of droplets exhaled in human breath, three unique nucleic acid samples were added to three personal humidifiers at different locations at varied distances from the Bubbler in a room with high airflow and a room with low airflow. Although a detailed exploration of this application was beyond the scope of the study, the results demonstrate the potential to use aerosolized nucleic acids to quantitatively map airflow in indoor spaces, and to detect SARS-CoV-2 in the air.

“Such technology could be useful in restoring service to industries such as hotels, cruise ships and casinos,” Fairbrother said. “There is also an epidemiological benefit to routine testing of air at early warning sites such as transportation hubs and hospital emergency departments.”

Other Brown University contributors to this study include Chaorui Duan, Luke Buerer, Jing Wang, Gavin Sabalewski, Gregory D. Jay, Sean F. Monaghan and Andrea E. Arena. The research was supported by National Institute of General Medical Sciences grants R01GM105681 and R01GM127472, and the Roddy Foundation grant GR5290840.