COVID-19 is known to be transmitted mainly by respiratory droplets. This is the reasoning behind physical distancing, since it’s hard for those droplets to travel more than a few feet. But scientists are debating whether very small droplets, small enough to float through the air, are common enough and infectious enough to be a serious risk.
The nature of a brand-new virus is that messages about prevention have to go out to the public before we have all the information. It may take years to fully understand how the virus most commonly spreads. We do not know, for sure, whether tiny aerosol droplets can spread the coronavirus, but the New York Times reports that over 200 scientists are writing a letter to the World Health Organisation urging them to consider changing their recommendations to account for transmission via these droplets. (These droplets don’t meet the WHO’s definition of an “airborne” disease like measles, which can hang in the air for hours, but the scientists argue that the difference is still important.)
If it’s true that small floating droplets are a significant source of transmission, that doesn’t mean that everything we know is wrong, just that certain things are even more important than we realised.
So here’s what would change if we could confirm that small droplets are an important source of transmission:
Physical distancing would still be important
For example: distancing may protect us less than we thought it did. Staying 1.5 metres away from somebody means that we are avoiding those larger respiratory droplets that come from breathing and coughing.
But if the smaller droplets can travel and infect people, that means that standing just outside that 1.5 m radius may still put you at risk. To repeat, this is a change in emphasis, not a complete reversal. Nobody ever said that the 1.5 m rule was a guarantee. But it may be that the rule provides less protection than we thought.
We should avoid indoor spaces even more
Outdoors, fresh air circulates and those tiny droplets can float away on the breeze. Indoors, they hang in the air without an obvious escape route.
Ventilating indoor spaces should help. That means opening windows, or running an air circulation system, ideally with a filter. But if aerosols are a significant source of transmission, the bigger take-home message would be that indoor spaces may be inherently risky. Aerosols are the reason why gatherings with singing and shouting, like church services, may be so problematic.
N95 masks would be needed more urgently
We already know that medical masks protect better than cloth masks, and N95s protect better than procedure masks with ear loops.
If the virus is transmitted through those tiny droplets, cloth and procedure masks are doing even less than we thought. In that case, we should possibly all be wearing N95s. Unfortunately, supplies are still low. The recommendation to wear “cloth face coverings” (and surgical masks, when available) is based on freeing up those N95s for healthcare workers. That’s still a problem, but the shortage becomes an even bigger problem if it turns out that our homemade masks aren’t working as well as we thought.