Opinion | Yes, the #Coronavirus Is in the Air - The New York Times
I agree that long-range transmission by aerosols probably is not significant, but I believe that, taken together, much of the evidence gathered to date suggests that close-range transmission by #aerosols is significant — possibly very significant, and certainly more significant than direct droplet spray.
The practical implications are plain:
Social distancing really is important. It keeps us out of the most concentrated parts of other people’s respiratory plumes. So stay away from one another by one or two meters at least — though farther is safer.
Wear a mask. Masks help block aerosols released by the wearer. Scientific evidence is also building that masks protect the wearer from breathing in aerosols around them.
When it comes to masks, size does matter.
The gold standard is a N95 or a KN95 respirator, which, if properly fitted, filters out and prevents the wearer from breathing in at least 95 percent of small aerosols.
The efficacy of surgical masks against aerosols varies widely.
One study from 2013 found that surgical masks reduced exposure to flu viruses by between 10 percent and 98 percent (depending on the mask’s design).
A recent paper found that surgical masks can completely block seasonal coronaviruses from getting into the air.
To my knowledge, no similar study has been conducted for #SARS-CoV-2 yet, but these findings might apply to this virus as well since it is similar to seasonal coronaviruses in size and structure.
My lab has been testing cloth masks on a mannequin, sucking in air through its mouth at a realistic rate. We found that even a bandanna loosely tied over its mouth and nose blocked half or more of aerosols larger than 2 microns from entering the mannequin.
We also found that especially with very small aerosols — smaller than 1 micron — it is more effective to use a softer fabric (which is easier to fit tightly over the face) than a stiffer fabric (which, even if it is a better filter, tends to sit more awkwardly, creating gaps).
Avoid crowds. The more people around you, the more likely someone among them will be infected. Especially avoid crowds indoors, where aerosols can accumulate.
Ventilation counts. Open windows and doors. Adjust dampers in air-conditioning and heating systems. Upgrade the filters in those systems. Add portable air cleaners, or install germicidal ultraviolet technologies to remove or kill virus particles in the air.
It’s not clear just how much this coronavirus is transmitted by aerosols as opposed to droplets or via contact with contaminated surfaces. Then again, we still don’t know the answer to that question even for the flu, which has been studied for decades.
But by now we do know this much: Aerosols matter in the transmission of #Covid-19 — and probably even more so than we have yet been able to prove.