In Quillette, assistant editor Jonathan Kay publishes an important analysis based on contact tracing of 54 documented superspreader events early in the epidemic:
COVID-19 Superspreader Events in 28 Countries: Critical Patterns and Lessons
written by Jonathan Kay
Jonathan Kay is Canadian Editor of Quillette. He tweets at @jonkay.
… I was struck by how few of the SSEs originated in conditions stereotypically associated with the underclass (though a March outbreak at a Qatari migrant workers camp in the industrial area north of Doha offers one such example). Many of the early SSEs, in fact, centered on weddings, birthday parties, and other events that were described in local media as glamorous or populated by “socialites.” …
But absent more data, the more obvious explanation is that these early SSEs are linked to the intercontinental travel practices of the guests. … Moreover, COVID-19 outbreaks in poor communities are simply less likely to be reported, because the victims have less access to testing, high-end medical care, or media contacts.
In fact, the 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:
- Of the 54 SSEs on my list for which the underlying activities were identified, no fewer than nine were linked to religious services or missionary work. …
- Nineteen of the SSEs—about one-third—involved parties or liquor-fueled mass attendance festivals of one kind or another, including (as with the examples cited above) celebrations of weddings, engagements and birthdays.
- Five of the SSEs involved funerals.
- Six of the SSEs involved face-to-face business networking. This includes large-scale events such as Biogen’s notorious Boston leadership meeting in February, as well as one-on-one business meetings—from the unidentified “traveling salesperson” who spread COVID-19 in Maine to Hisham Hamdan, a powerful sovereign-wealth fund official who spread the disease in Malaysia.
All told, 38 of the 54 SSEs for which activities were known involved one or more of these four activities—about 70 percent….
But even that 70 percent figure underestimates the prevalence of these activities in COVID-19 SSEs, because my database also includes five SSEs involving two warships and three cruise ships—the USS Roosevelt, Charles de Gaulle, Diamond Princess, Grand Princess and Ruby Princess—at least three of which (and probably all five) featured onboard parties.
These parties, funerals, religious meet-ups and business networking sessions all seem to have involved the same type of behaviour: extended, close-range, face-to-face conversation—typically in crowded, socially animated spaces. This includes the many people infected by a bartender while being served at a raucous après ski venue in Austria, and party guests in Brazil greeting “each other with two kisses on the cheek [a local custom], hugs and handshakes.” The funerals in question are generally described as highly intimate and congested scenes of grieving among close friends and relatives. In the case of the SSE funeral in Albany, Georgia that devastated the local population, “people wiped tears away, and embraced, and blew their noses, and belted out hymns. They laughed, remembering. It was a big gathering, with upward of 200 mourners overflowing the memorial chapel, so people had to stand outside.”
With few exceptions, almost all of the SSEs took place indoors, where people tend to pack closer together in social situations, and where ventilation is poorer. (It is notable, for instance, that the notorious outbreak at an Austrian ski resort is connected to a bartender and not, say, a lift operator.) But generalizations in this area are complicated by the fact that some of the religious festivals described herein were mixed indoor/outdoor affairs. Moreover, the February 19 SSE at San Siro stadium in Milan is also ambiguous, since that stadium has a roof over the seating area, but not over the field.
I would imagine that supporters of the Bergamo soccer club tended to travel to the big game in Milan in buses and trains with other supporters, talking and perhaps singing excitedly at least one way. (If Bergamo won, then both ways.)
The media accounts of these SSEs are full of descriptions in this vein. At a February 15 festival in Gangelt, a town in Germany’s tiny Heinsberg district, “beer and wine flowed aplenty as approximately 350 adults in fancy dress locked arms on long wooden benches and swayed to the rhythm of music provided by a live band. During an interval in the programme, guests got up to mingle with friends and relatives at other tables, greeting each other as Rhineland tradition commands, with a bützchen, or peck on the cheek.” Since that time, more than 40 Germans from the Heinsberg district have died. It’s been called “Germany’s Wuhan.”
In the case of religious SSEs, Sikhs, Christians, Jews and Muslims are all represented in the database. …
Of the 54 SSEs for which underlying activities could be identified, only 11 did not involve either religious activity, a party, a funeral, a cruise or extended face-to-face professional networking. But even in this minority of cases, one can observe almost identical interpersonal dynamics. Three of the SSEs—in Japan, Skagit County, WA, and Singapore—involved concert-goers and singing groups belting out tunes together over a period of hours. (The Skagit example [a Presbyterian choir practice] is particularly interesting, because the organizers were aware of the COVID-19 risk beforehand, and took the precaution of spacing out the participants by several feet. If they had been merely chatting, instead of singing, no one might have gotten sick.)
Another SSE involved a group of Canadian doctors engaged in a day of recreational curling. This is a sport that involves hyperventilating participants frenetically sweeping the ice with brooms while their faces are positioned inches apart, sometimes changing partners—an ideal climate for Flüggian infection. Indeed, this partner-swapping aspect of the activity seems to be a common feature of many suspected SSEs, such as square-dancing parties.
Four of the SSEs were outbreaks at meat-processing plants, in which “gut snatchers” and other densely packed workers must communicate with one another amidst the ear-piercing shriek of industrial machinery. I lack the expertise to determine how the refrigerated nature of some meat-processing facilities may affect the dynamics of droplet transmission—though I would also note that at least four of the SSEs on my list unfolded at European ski resorts. But high levels of noise do seem to be a common feature of SSEs, as such environments force conversationalists to speak at extremely close range. (Related factors may be at play in old-age homes. These tend to be quiet places. But the reduced speaking volume and hearing functions of some elderly residents lend themselves to conversations held at much closer range than is socially typical in the general population.)
Finally, three of the SSEs involved mass sports spectacles, during which fans regularly rain saliva in all directions as they communally celebrate or commiserate in response to each turn of fortune. (Advance to the 8:30 mark of this video, showing euphoric hometown fan reaction during the infamous February 19th football match between Atlanata and Valencia, and you will see exactly what I mean.) As we now know, the danger starts even before the action begins: One of the most dangerous things you can do at a sports event in the COVID-19 era is sing the national anthem.
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When do COVID-19 SSEs happen? Based on the list I’ve assembled, the short answer is: Wherever and whenever people are up in each other’s faces, laughing, shouting, cheering, sobbing, singing, greeting, and praying.
“Humanist Conan, what is best in life?”
“Wherever and whenever people are up in each other’s faces, laughing, shouting, cheering, sobbing, singing, greeting, and praying.”
I imagine kissing should also be included in this list.
This is depressing. The accumulating evidence appears to be that most of the grimmer economic activities, outside of perhaps taking the NYC subway to work, aren’t all that dangerous, but the social activities that make getting and spending much more worth living are.
Basically, activities that a Boston Puritan minister of 1650 would have approved of, such as many forms of making money and listening attentively to his sermons, seem less dangerous, while the more dangerous activities are what we tend to think of as either fun or cathartic.
… It’s worth scanning all the myriad forms of common human activity that aren’t represented among these listed SSEs: watching movies in a theater, being on a train or bus, attending theater, opera, or symphony (these latter activities may seem like rarified examples, but they are important once you take stock of all those wealthy infectees who got sick in March, and consider that New York City is a major COVID-19 hot spot). These are activities where people often find themselves surrounded by strangers in densely packed rooms—as with all those above-described SSEs—but, crucially, where attendees also are expected to sit still and talk in hushed tones.
People are all tending to face in the same direction in these venues. And even during intermission, they mostly speak to the people they came with, not to random non-householders.
The world’s untold thousands of white-collar cubicle farms don’t seem to be generating abundant COVID-19 SSEs—despite the uneven quality of ventilation one finds in global workplaces. This category includes call centers (many of which are still operating), places where millions of people around the world literally talk for a living. (Addendum: there are at least two examples of call-centre-based clusters, both of which were indicated to me by readers after the original version of this article appeared—one in South Korea, which overlaps with the massive Shincheonji Church of Jesus cluster; and the other in Jamaica.)
In New Zealand, one SSE centered on students at a girls’ school. Given the exuberant and socially intimate way in which children laugh, argue and gossip, I am surprised there are not more schools on my list. Moreover, I had trouble finding any SSEs that originated in university classrooms, which one would expect to be massive engines of infection if COVID-19 could be transmitted easily through airborne small-droplet diffusion.
In the United States, the two university-based examples that have received the most media attention are Liberty University in Lynchburg, Va. and the University of Texas. But in neither case was there any apparent connection to classroom activity. At Liberty, where several employees got sick, the one student known to be infected isn’t even currently enrolled in classes. And the UT outbreak, which has caused more than 40 students to be infected, actually took place on a Spring Break trip to Mexico. It’s possible, I suppose, that these students spent the week holed up in a conference room with a stack of books. But my instincts indicate otherwise.
It’s similarly notable that airplanes don’t seem to be common sites for known SSEs, notwithstanding the sardine-like manner in which airlines transport us and the ample opportunity that the industry’s bureaucracy offers for contact tracing. Yes, New Zealand has one cluster that’s based around an infected but asymptomatic flight attendant. But the many known infections he caused took place at a wedding reception, not in an airplane. …
I’ve already cataloged the limitations of my approach at some length. And I will emphasize again that I am not an epidemiologist, virologist, or infectious-diseases expert (though I like to think I’ve made myself a somewhat educated reader of the most recently published scientific literature in these fields). But even a layperson can see that there is a fairly clear pattern in the most notorious, destructive, and widely reported cases of mass COVID-19 infection—virtually all of which feature forms of human behaviour that permit the direct ballistic delivery of a large-droplet Flüggian payload from face A to face B. If fomites were a major pathway for COVID-19 infection outside of hospitals, old-age residences, and homes, one would expect restaurant cooks, mass-transit ticket handlers, and FedEx delivery workers to be at the center of major clusters. They’re not. If small-droplet airborne concentrations in unventilated spaces were a common vector for COVID-19 transmission (as with measles, for instance), one would expect whole office buildings to become mass-infection hot spots. That doesn’t seem to have happened. …
Fighting this disease will always be hard. But it will be harder still if we fail to develop a proper understanding of the precise way it attacks us.
An important unresolved question is if there is a selection bias in these list of superspreader events. For example, imagine that NYC subways were an important avenue of infection. But imagine how much harder a problem the subway poses for contract tracers than, say, a wedding reception with an official invite list.