It’s the variation that may mystify you

This week, Zeynep Tufekci in The Atlantic described a characteristic of the Covid pandemic that should influence public health policies and individual practices.   The article has been flagged by two different friends on opposite sides of the country in the past 24 hours.  

My friends and I have learned over the years that systems often require insight into both average behavior and variation in that behavior.   We love finding compelling examples.

Tufekci’s non-technical article clearly describes how important it is to understand the variation (dispersion) in the disease’s natural history.

“… averages aren’t always useful for understanding the distribution of a phenomenon, especially if it has widely varying behavior. If Amazon’s CEO, Jeff Bezos, walks into a bar with 100 regular people in it, the average wealth in that bar suddenly exceeds $1 billion. If I also walk into that bar, not much will change. Clearly, the average is not that useful a number to understand the distribution of wealth in that bar, or how to change it. Sometimes, the mean is not the message. Meanwhile, if the bar has a person infected with COVID-19, and if it is also poorly ventilated and loud, causing people to speak loudly at close range, almost everyone in the room could potentially be infected—a pattern that’s been observed many times since the pandemic begin, and that is similarly not captured by R [the average number of people infected by an individual with the disease]. That’s where the dispersion comes in.”

In other words, it appears that the COVID-19 spreads non-uniformly:  superspreading events account for most of the cases.  

Tufekci summarizes views of several experts, across multiple countries.  She concludes that a focus on prevention of superspreading events—reducing or eliminating the frequency of “crowds in closed spaces in close contact, especially if there’s talking or singing”—is a fundamental intervention.   Japanese experts early on recognized the variation in COVID-19 spread and took appropriation action to prevent super-spreading events.

I gave a climate-change example of the impact of variation in this post, “It’s the variation that will hurt you.”