A modeling study raises questions about how far droplets, like those that carry the virus that causes COVID-19, can travel before becoming harmless.

Experiments dating to the 1930s proposed two paths for respiratory droplets like those from a sneeze or cough. Either they are big and heavy, plummeting to the ground without much chance of infecting another person. Or they are so small and light that they dry out almost instantly, remaining airborne but becoming harmless very quickly. The dryness renders «enveloped» viruses like coronaviruses unable to infect.

But a new study from scientists at the Department of Energy’s Pacific Northwest National Laboratory suggests a third option — that small respiratory particles can remain moist and airborne for a longer time and greater distance than scientists have recognized.

«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 findings were published in the February issue of the journal International Communications in Heat and Mass Transfer.

«The idea that enveloped virions may remain well hydrated and thus fully infective at substantial distances is consistent with real-world observations. Perhaps infectious respiratory droplets persist longer than we have realized,» Pease added.

The PNNL team took a long look at the mucus that coats the respiratory droplets that people spew from their lungs. Scientists know that mucus allows many viruses to travel further than they otherwise would, enabling them to journey from one person to another.

Story Source:
Materials provided by DOE/Pacific Northwest National Laboratory. Original written by Tom Rickey. Note: Content may be edited for style and length.