Sturgis Motor-Bike Rally: Superspreader Event, Or SuperDUPERspreader Event?

Friendly Sturgis is open for business!

This year's annual Sturgis Motorcycle Rally in South Dakota, held over 10 days in early August, might be the biggest superspreader event in the US coronavirus pandemic, according to a new study published by San Diego State University's Center for Health Economics & Policy Studies. Using cellphone data and rates of infection in areas where lots of Sturgis attendees returned to, the researchers project that as many as 260,000 new cases nationwide may have resulted from the rally, if you factor in both the people who were infected at the rally and those they went home and infected.

The study also estimates that, based on the average cost of treating a case of COVID-19, the total medical price tag for the Sturgis infections comes to $12.2 billion. At that rate, the paper said, "This is enough to have paid each of the estimated 462,182 rally attendees $26,553.64 not to attend." And to think, millions of Americans didn't go for free! 

That's a hell of a lot more than the 260 cases the Washington Post   identified last week by surveying local health departments across the country, or the 124 cases in South Dakota the state Department of Health has officially listed. South Dakota officials were quick to say the SDSU report couldn't possibly be true, because it just can't be — how could an event that attracted over 460,000 people who were closely crammed together in a bunch of locations, usually without masks, possibly have spread that much virus? Especially since, as South Dakota GOP Governor Kristi Noem has said all along, it's about personal decisions and freedom? Those are much more scientific terms than whatever a bunch of eggheads say, because this is America. Read your Constitution, nerds!

Now, as South Dakota officials point out, it's true the study has not yet gone through a formal peer review process, so maybe there will turn out to be something terribly off in its methodology, which BuzzFeed News summarizes so you can understand it.

The researchers looked at county-level data on new confirmed COVID-19 cases, as well as anonymized cellphone tracking data released by the company SafeGraph. This included the recorded home location for each phone, allowing the researchers to determine how many attendees came from each county across the nation.

They then compared the trajectory of cases in counties with many Sturgis attendees, such as Clark County, Nevada, and Maricopa County, Arizona, to those with previously similar case trajectories that had few residents who traveled to Sturgis. This allowed the researchers to estimate the number of new cases resulting from exposure to the coronavirus during the rally — including cases caused by secondary transmission after attendees returned home. Extrapolating to rallygoers nationwide gives the figure of more than 260,000 new coronavirus cases caused by the Sturgis gathering.

Saskia Popescu, an epidemiologist at University of Arizona (in Tucson, not "Phoenix," Buzzfeed ), called the research "compelling," and Noah Haber, a research methodology expert at Stanford, said he didn't see any obvious problems with the research design, but cautioned with a lot of science words about how it really would need a very close examination by other researchers to see if it holds up, which is how science works.

One of the co-authors of the study, Andrew Friedson, a health economist at the University of Colorado, Denver, told BuzzFeed the 260,000 cases resulting from Sturgis account "for 19% of the national cases over this time period. [...] That's huge."

South Dakota health officials had few qualms about casting doubt on the study, emphasizing it hasn't been peer-reviewed (which is worth keeping in mind, but doesn't mean "dismiss this" any more than a news outlet locating a major university in the wrong city). State epidemiologist Joshua Clayton said the paper's findings "do not align with what we know of the impacts of the rally among attendees in the state of South Dakota." He said the researchers didn't account for factors like "an already increasing trend of cases" in South Dakota, or the fact that schools and colleges have been reopening, how about that, hmm? That latter may be a valid point, but since the study compared the counties with lots of Sturgis-goers to other counties from which few people went to Sturgis, we would guess schools and colleges were also opening in those counties?

Clayton also said the state has determined that only 124 South Dakota residents attended the rally before being diagnosed with COVID-19, but acknowledged the state isn't including possible secondary infections in its data — those are the people who might not have gone to the rally, but were infected with the virus by someone who did. Friedson told BuzzFeed that while cases in South Dakota had indeed been increasing prior to the rally, new cases per day sharply increased in the weeks after Sturgis, causing a spike of more than 3,000 cases in South Dakota, by the study's estimate. He added that

self-reports like those used by the state's health department are unreliable because people may not report accurately. Such reports also don't account for other people attendees may have infected. "You cannot rely on these types of reports to tell you the number of cases[.]"

Governor Noem wasn't bothered at all by the report, which is unsurprising because she has yet to give two ripe shits about science anyway. In a two-paragraph statement, Noem dismissed the SDSU study completely, saying it "isn't science; it's fiction." She went on:

Under the guise of academic research, this report is nothing short of an attack on those who exercised their personal freedom to attend Sturgis. [...] Predictably, some in the media breathlessly report on this non-peer reviewed model, built on incredibly faulty assumptions that do not reflect the actual facts and data.

At one point, academic modeling also told us that South Dakota would have 10,000 COVID patients in the hospital at our peak. Today, we have less than 70. I look forward to good journalists, credible academics, and honest citizens repudiating this nonsense.

See what happens when you don't build "personal freedom" into your science, guys? You end up with very bad numbers! And if one statistical model is inaccurate, they all are. That's just science.

Mind you, even if the SDSU study turns out to have been off by a ridiculous amount — let's arbitrarily say the real number of infections rippling out from Sturgis is just a quarter of the researchers' estimate — that would still be tens of thousands of cases nationwide, and hundreds more than the state health department estimate.

Enjoy your coronavirus, America, some people are determined to make sure it's never brought under control.

[ Buzzfeed News / WaPo / Rapid City Journal/ "The Contagion Externality of a Superspreading Event: The Sturgis Motorcycle Rally and COVID-19" ]

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