What’s a ‘Superspreader’ Event, Really?
How an epidemiologist thinks about ‘superspreading,’ a term with no clear definition
Thanks to the Covid-19 pandemic, the term “superspreader” has become a normal part of our everyday vocabulary. Since its emergence in the coronavirus conversation around the end of May, it’s been used to describe events like weddings, motorcycle rallies, and choir practice — any event in which a small number of people are responsible for infecting a far larger group with Covid-19. Most recently, it’s been used to describe a celebration held for Supreme Court nominee Amy Coney Barrett in the White House’s Rose Garden on September 26: At least eight of the White House officials in attendance, including the president, have now tested positive for Covid-19. Photos from the so-called “superspreader” event show lots of hugging and few masks.
But for a word that’s used so often, it isn’t very clearly defined.
“I don’t think there is a single agreed-upon definition, and to some extent, it is going to be variable from pathogen to pathogen,” says Jon Zelner, PhD, an assistant professor of epidemiology in the University of Michigan School of Public Health, in an email to the Medium Coronavirus Blog. There is likewise no set rule for determining whether a person is a superspreader.
That’s not to say that the term doesn’t refer to something real — just that its definition is relative and that our baseline for comparison may shift as we learn more about Covid-19.
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One way to think about it is as a deviation from the baseline pattern of spreading. So far, scientists have observed that most people with Covid-19 don’t infect that many other people. Zeynep Tufekci, writing in The Atlantic, recently observed: “Multiple studies from the beginning have suggested that as few as 10–20% of infected people may be responsible for as much as 80–90% of transmission, and that many people barely transmit it.” So, as Zelner explains, “it may well be that heterogeneity in transmission is…