Airborne Coronavirus particles may travel farther than thought: Lab Study

US: Small coronavirus respiratory particles may remain moist and airborne for a longer time and travel to greater distance than previously thought, a study conducted in a laboratory suggests.

The research, published in the journal International Communications in Heat and Mass Transfer, took a long look at the mucus that coats the respiratory droplets that people spew from their lungs.

The researchers from the US Department of Energy’s Pacific Northwest National Laboratory (PNNL) noted that mucus allows many viruses to travel further than they otherwise would, enabling them to journey from one person to another. Conventional wisdom has been that very small, aerosolised droplets of just a few microns, like those produced in the lungs, dry out in air almost instantly, becoming harmless.

However, the PNNL team found that the mucus shell that surrounds respiratory droplets likely reduces the evaporation rate, increasing the time that viral particles within the droplets are kept moist.

Since enveloped viruses like SARS-CoV-2 have a fatty coating that must be kept moist for the virus to be infectious, the slower evaporation allows viral particles to be infectious longer. The team estimates that droplets encased in mucus could remain moist for up to 30 minutes and travel up to about 200 feet.

“There are reports of people becoming infected with a coronavirus downwind of an infected person or in a room several minutes after an infected person has exited that room,” said Leonard Pease, the corresponding author of the study. The team also found that increasing ventilation rapidly reduced particle levels in the source room.

However, particle levels in the other connected rooms jumped immediately; levels spiked 20 to 45 minutes later with vigorous air changes increasing the spike. – NDTV