A growing body of research shows that SARS-CoV-2, the virus that causes COVID-19, can spread from person to person through the air. Indoor spaces with poor ventilation in areas where the virus is prevalent are particularly hazardous.
In the fictional world of “Star Trek,” public health officials and first responders would be able to determine instantly if space had a dangerous concentration of airborne virus, and any other pathogen, by simply waving around a tricorder.
That technology, imagined 60 years ago, is still firmly in the realm of fiction. However, devices that can rapidly detect particular airborne pathogens – including SARS-CoV-2 – are in the works in various research laboratories.
The air we breathe
Detection of the presence of airborne virus particles is complicated by the mixture of other particles in the air. The atmosphere includes a large number of floating particles, a significant fraction of which are biological. Typically, with each breath, you inhale about a thousand biological particles.
These bioaerosols include live and dead organisms, including viruses, bacteria, fungi, pollen and plant and animal debris. Viruses are the smallest of these particles. They range in size from 10 to 300 nanometers, or millionths of a millimetre. In contrast, red blood cells average about 6 to 8 microns, or 6,000 to 8,000 nanometers, in diameter. Bacteria range from 1 to 4 microns and fungi 5 to 10 microns. Plant and animal debris is generally larger than 10 microns.
Most of these biological particles are not a health concern, because most are bits of plants and animals, including humans. However, it only takes a small number of dangerous microbes to produce a pandemic.
Despite these advances, there is still a lot of work to be done to be able to instantly identify the presence of pathogens in the air. Current techniques for identifying microbes are expensive, require specialized equipment and involve long processing steps. They also can’t detect a species from small amounts of genetic material.
Recent advances, however, provide some promise for the development of sensors that can provide quick information about bioaerosols.
One approach uses laser-induced fluorescence. In this technique, particles are illuminated with light of a particular colour or wavelength, and only biological particles respond by fluorescing, or emitting light. This technique can be used to identify and quantify the presence of biological particles in the air in real-time but it doesn’t differentiate between a safe and a harmful microbe.
Another advance is using mass spectrometry for bioaerosol detection. In this technique, a single bioaerosol particle is blasted apart with a laser and the molecular fragments are immediately analyzed to determine the molecular composition of the particles. Researchers are also using Raman spectroscopy-based sensors. Raman spectroscopy can identify molecular composition from light reflected off of samples without destroying the samples.