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Superspreaders Explained

They’re people who pass on infection to many others, and knowing their common traits can help you, argues journalist Jonathan Kay in the latest episode of Eat Move Think

A crowd of people at an entertainment hub enjoy themselves.

Link to podcast transcript

Why do some large gatherings of people become superspreader events, while some do not? Jonathan Kay is a Canadian journalist who recently wrote a fascinating article on the science of superspreaders that draws on his background studying fluid dynamics during his master’s degree in metallurgy at McGill. He’s also both a tennis and board-game enthusiast — the former, a pastime he recommends, and the latter, a pastime he recommends against, as it falls into his list of “superspreader” activities. His insights can help all of us return to work more safely. Listen to Eat Move Think on Apple Podcasts, Spotify, Google Play or your favourite podcast platform. And in the meantime, following are four of the key points that Kay made during his conversation with Medcan CEO Shaun Francis.

Masks stop the spread.

In 1899, German bacteriologist Carl Flügge proved that microbes, and the infections they cause, can be transmitted ballistically through large droplets expelled at high velocity from the mouth and nose. The question today is whether COVID-19 is spread by these so-called “Flügge droplets,” or the comparatively more microscopic aerosol particles that can spread more contagious disease, such as measles. Kay argues the evidence suggests that COVID-19 is spread by Flügge droplets. Masks are not effective at preventing the spread of disease transmitted by aerosol particles — but they do help prevent spread of disease transmitted by Flügge droplets. If COVID-19 is transmitted via Flügge droplets, as Kay argues, wearing a mask would be an effective way to prevent infecting others.

It’s not the size of the event, but the behaviour of the attendees

that matters when spreading COVID-19. Sporting events, concerts, even church gatherings — all of these large get-togethers have one thing in common: hordes of people in close quarters, their faces often mere inches from one another while they yell, sing, cheer or laugh out loud. COVID-19, Kay argues, is spread through the person-to-person transfer of large droplets, which can happen during coughing, sneezing or when people are speaking loudly to one another with their faces close. His research into how COVID-19 spreads also explains why so many superspreader events occur in old-age and retirement homes, where elderly residents tend to have difficulty hearing, and thus, caregivers, relatives and friends tend to speak more loudly, and more closely to the residents’ faces.

Not all large gatherings of people are dangerous.

Kay found that comparatively few superspreader events happen in office towers, on planes or trains, or in movie theatres — confined spaces, yes, but also places where people typically speak in lowered voices. One case Kay cites features an Air New Zealand flight attendant who infected 15 people at a party he attended — but not a single passenger on the flight he worked that very same day. Why? Kay argues it’s because on planes people tend to speak quietly and act in a reserved manner. In contrast, the party would have seen the flight attendant speaking loudly with his face quite near other peoples’. The theory features public policy implications, suggesting that sporting events, concerts and large funeral gatherings pose a large risk for COVID-19 superspreading, while office work, retail shopping and cinema attendance may not.

COVID-19 has a butterfly effect.

The term butterfly effect refers to a phenomenon that sees the flapping of a single butterfly’s wings causing enormous consequences later on. But with COVID-19, we’re talking about social butterflies. Outgoing people tend to bounce between numerous social groups, hugging, kissing and laughing while they do. In South Korea, doctors tracked the movements of a superspreader referred to as Patient 31. During the course of one weekend she came in contact with more than 1,000 people — and South Korea’s number of infected cases went from 30 to 2,300 in just 10 days. The point? Even a single person’s movements can trigger enormous effects.


Please subscribe and rate us on your favourite podcast platform. Follow Jonathan Kay on Twitter @jonkay. Eat Move Think host Shaun Francis is Medcan’s CEO and chair. Follow him on Twitter @shauncfrancis. Connect with him on LinkedIn. And follow him on Instagram @shauncfrancis. Eat Move Think is produced in conjunction with Ghost Bureau.

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