“Mater Artium Necessitas”

So said William Horman, 16^th century Headmaster of the Eton school. Translated, he posited, “The mother of invention is necessity.”

And necessity these days means environmental screening for SARS-CoV-2. Room air samplers have been developed and used to detect airborne virus RNA in large settings, such as hospitals and other large buildings people frequent. In fact active environmental air samplers have been used outdoors to detect airborne DNA and RNA as a way to survey animal populations in the wild. These are fairly large, immobile, active air samplers that require electricity to power them and crews to maintain them. While useful, environmental samplers are limited by their power requirements, lack of mobility, cost, and maintenance needs.

So, the mother of invention led to a portable, passive, personal air sampler that can be worn on one’s collar tool as described in a recent paper. It was reported to be quite effective for detecting ambient exposure to aerosol and droplet CoV-2 in the air.

The device uses a polydimethylsiloxane (PDMS)-based passive air sampler, which previously has been used to capture hydrophobic chemical contaminants and other nonpolar compounds, such as lipid-enveloped viruses that stick to the polymeric surface. After laboratory testing under controlled conditions that determined the unit could detect sub-infectious levels of virus exposure, samplers were passed out to select community members across Connecticut to surveil personal CoV-2 exposure. The study reported that 21% of wearers working in indoor restaurant settings, and 9% working in homeless shelters were exposed to 4-112 copies of CoV-2 per cubic meter of air. No exposure was reported for healthcare workers or “community members” who did not work in putative high-risk environments. The authors surmised that the lack of exposure by healthcare workers was due to the strict sterilization and hygiene procedures used in clinics and hospitals.

While the monitors did a good job sampling ambient air in real time, the need to later analyze the sample by RT-PCR for the presence of viral particles means that the results are not obtained in real time. This is a bit of a drawback to the current personal samplers.

Bottom line. These PDMS-based passive samplers may serve as a useful exposure assessment tool for airborne viral exposure in real-world high-risk settings and allow early detection of potential cases and guidance on infection control. More broadly, this also could be used to monitor the presence of other biological scourges in public places and serve as early warning devices for biological warfare threats.

Necessity is indeed the mother of invention.

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