In the early weeks of the pandemic, we were inundated with reminders to “wash our hands”. It was said that 20 or even 30 seconds of thorough scrubbing was needed to kill any particles that might be lurking there.
And we were treated to some rather patronising instructional videos. You’d assume that most adults were already familiar with the concept of hand-washing. (Telling us to “be thorough” would probably have sufficed).
Yet more and more evidence emerged that surfaces (known in the medical jargon as “fomites”) are not an important mode of transmission for SARS-CoV-2. Which is not to say you shouldn’t wash your hands.
However, there was still a dispute over whether respiratory droplets or airborne particles play a greater role in viral spread. Droplets are transmitted over short distances, and fall to the ground quickly. (Hence the ‘2m rule’.) Airborne particles, on the other hand, can remain aloft for minutes or even hours, and travel much greater distances.
Over the last couple of months, it’s become clear that COVID is primarily transmitted via airborne particles. (Though some would say this was clear as early as the Diamond Princess outbreak, when several hundred passengers caught the virus on a cruise ship.)
In a recent article for the New York Times, the science writer Zeynep Tufekci reviews the debate over the transmission of SARS-CoV-2 and explains how mistaken assumptions led to errors in pandemic management.
She begins by noting it was only on April 30th this year that the WHO finally updated its website to indicate that COVID is transmitted via both droplets and airborne particles. Until then, it simply had claimed, “the main way the virus spreads is by respiratory droplets”.
If the importance of aerosol transmission had been accepted early, we would have been told from the beginning that it was much safer outdoors, where these small particles disperse more easily, as long as you avoid close, prolonged contact with others. We would have tried to make sure indoor spaces were well ventilated, with air filtered as necessary.
This also implies that plastic shields – which you might have seen in your local gym or supermarket – do essentially nothing to prevent transmission:
There was no attention to ventilation, installing air filters as necessary or even opening windows when possible, more to having people just distancing three or six feet, sometimes not requiring masks beyond that distance, or spending money on hard plastic barriers, which may be useless at best. (Just this week, President Biden visited a school where students were sitting behind plastic shields.)
Indeed, one of the safest places to be during the pandemic is outdoors. (As I’ve noted before, the vast majority of infections occur in indoor spaces.) This raises serious questions about the Government’s stay-at-home order, which confined us to our homes for weeks, with only one form of outdoor exercise per day.
Particularly absurd was when police forces used drone footage to shame people who were out walking in the countryside (most likely from indoor offices where the risk of transmission was far higher.)
If COVID mainly spreads via airborne particles, then telling people not to go outside doesn’t really make sense. And in fact, a study published in Proceedings of the National Academy of Sciences examined shelter-in-place orders in the United States, but did “not find detectable effects of these policies on disease spread or deaths.”
Tufekci compares the lack of attention to airborne transmission of COVID with our misunderstanding of cholera’s spread in the era before John Snow:
So much of what we have done throughout the pandemic — the excessive hygiene theater and the failure to integrate ventilation and filters into our basic advice — has greatly hampered our response. Some of it, like the way we underused or even shut down outdoor space, isn’t that different from the 19th-century Londoners who flushed the source of their foul air into the Thames and made the cholera epidemic worse.
Tufekci’s article contains a lot of interesting details, and is worth reading in full.