Rather Than Destroy the Economy, Let's Avoid the Three C's

Wednesday, June 03, 2020

Yesterday, I learned of two separate pieces -- one by a layman at Quillette and another by two epidemiologists at The New York Times -- that focus on the phenomenon of "superspreading events" in the current pandemic. In the words of the second of these, "20 percent of Covid-19 cases accounted for 80 percent of transmissions."

Might a closer look at these events help individuals better evaluate their risks or evade the virus -- and help government officials make better policy choices in the future?

Yes and yes.

Both pieces draw essentially the same conclusions regarding how best to avoid infection, but what I like about the Quillette piece is that it takes the time to explain why this is happening. In part, it is due to the primary mode of transmission being droplets, which author Jonathan Kay reviews at the beginning of his piece, and which he determined to be important in part as follows:

... I have chosen to exclude SSEs [super spreading events--ed] that center on hospitals and old-age homes, despite the fact that in many countries (including Canada, where I live), these comprise the main spawning ground for COVID-19. This is because the purpose of this exercise is to gain information about the relative effects of three broad modes of COVID-19 transmission -- large droplets transmitted ballistically, persistent concentrations of tiny airborne droplets, and contaminated surfaces. In hospitals and old-age homes, all three of these mechanisms are almost invariably at play -- as these tend to be shared spaces full of commonly touched surfaces and close interpersonal contact among residents and staff. And so such SSEs serve to inflate the size of the database without providing assistance in isolating variables. The same principle is true of COVID-19 transmission within households (and possibly prisons), which is why I have excluded intra-household clusters as well. [bold added]
After further explanation and analysis, Kay notes:
[T]he truly remarkable trend that jumped off my spreadsheet has nothing to do with the sort of people involved in these SSEs, but rather the extraordinarily narrow range of underlying activities. And I believe it is on this point that a close study of SSEs, even one based on such a biased and incomplete data set as the one I've assembled in my lay capacity, can help us...
The activities are, in my opinion, narrower than Kay's explanation would lead me to believe: For example, he notes a lack of super-spreading events at theaters. Nevertheless, I think his general reasoning is sound and dovetails with the more scientific research summary provided by the Times.

That said, it is the Times piece which provides language that can better help us remember and implement the advice. It very helpfully notes how the Japanese -- who got their epidemic well under control without lockdowns -- conceptualize the behaviors and situations that lead to SSEs:
Confined and crowded and close, oh my! (Image by Jake Weirick, via Unsplash, license.)
It stands to reason, too, that a highly contagious person is more likely to spread the infection in a crowd (at a wedding, in a bar, during a sporting event) than in a small group (within their household), and when contact is extensive or repeated.

Transmission is more likely during gatherings indoors than outdoors. Simply ventilating a room can help. We believe that with the South Korean call-center cluster, the essential factor of transmission was the extent of time spent in a crowded office area.

Also consider this counterexample: Japan. The government recently lifted a state of emergency after controlling its epidemic without having put in place any stringent social distancing measures or even doing much testing. Instead, it relied on largely voluntary measures encouraging people to stay at home and advice to avoid overcrowding in public venues.

In essence, Japan adopted an anti-superspreading strategy. The approach was targeted at limiting what some researchers from Tohoku University have called the "three Cs": closed spaces, crowds and close contacts. [links omitted, bold added]
The last sentence of this paragraph is my take-home, and I hope public officials begin basing policy on this proven and freedom-preserving strategy going forward.

-- CAV

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