In the chaotic first few months of the Covid-19 pandemic, stores faced shortages of all kinds — toilet paper, canned food, and especially, cleaning supplies. With everyone scrubbing their groceries, mail, even library books, good luck finding antibacterial wipes or disinfectant sprays back then. That’s because public health advice in early 2020 focused on sanitizing surfaces, not protecting against a virus that could be spread through the air.
Much of that guidance could be traced back to the World Health Organization, which stated early on, and unequivocally, that Covid-19 was not an airborne disease. Even as evidence grew that coronavirus-laced particles could linger in the air indoors and infect people nearby, and researchers raised the alarm about the risks this posed to health care workers and the general public, the WHO didn’t acknowledge that Covid was airborne until late 2021.
Part of what took so long was an entrenched disconnect between how different kinds of scientists and physicians use words like “aerosol”, “airborne” and “airborne transmission.” Those differences sowed confusion and escalated into a series of ugly skirmishes on social media.
To address the confusion and the ensuing controversy, in November 2021, the WHO assembled a group of experts to update its formal guidelines for classifying the different routes that pathogens take from one person to another.
On Thursday, after more than two years of discussions, that group published a report outlining a new set of definitions that more accurately reflect the state of the science of disease transmission. The experts divided transmission into routes that involve direct contact through touching infected surfaces or other people and others that involve the air. The latter route was dubbed “through the air transmission” and was further subdivided into “direct deposition,” which refers to larger particles that strike the mucus membranes of
