Quote:
Confusingly, in public-health circles, the word airborne has a technical meaning that’s not just “carried through the air.” When people are infected with respiratory viruses, they emit viral particles whenever they talk, breathe, cough, or sneeze. These particles are encased in globs of mucus, saliva, and water. Bigger globs fall faster than they evaporate, so they splash down nearby—these are traditionally called “droplets.” Smaller globs evaporate faster than they fall, leaving dried-out viruses that linger in the air and drift farther afield—these are called “aerosols.” When researchers say a virus is “airborne,” like measles or chickenpox, they mean that it moves as aerosols. When the World Health Organization asserts that the new coronavirus is “NOT airborne,” it’s claiming that the virus instead spreads primarily through the close-splashing droplets, which either land directly on people’s faces or are carried to their faces by unwashed, contaminated hands.
Such messaging is “really irresponsible,” argues Don Milton, an expert in aerosol transmission at the University of Maryland. The scientific community doesn’t even agree about whether aerosol transmission matters for the flu, so “to say that after three months we know for sure that this [new] virus is not airborne is … expletive deleted,” he says. Milton and other experts who study how viruses move through the air say that the traditional distinction between big, short-range droplets and small, long-range aerosols is based on outdated science. Lydia Bourouiba of MIT, for instance, has shown that exhalations, sneezes, and coughs unleash swirling, fast-moving clouds of both droplets and aerosols, which travel many meters farther than older studies predicted. Both kinds of glob also matter over shorter distances: Someone standing next to a person with COVID-19 is more likely to be splashed by droplets and to inhale aerosols.
I'd say there's a couple of other factors at play too