Sturgis Motorcycle Rally Is Now Linked to More Than 250,000 Coronavirus Cases

[Moderate Right]

I have to say, while I am certain that Sturgis spread COVID-19 far and wide, attributing that many cases -- nearly 20% of all US cases during the study period -- sounds unlikely. It just seems a little too soon for those kind of numbers.

That said, it is somewhat sad that the state has to scramble to find other equally disturbing reasons why South Dakota's numbers rose in recent weeks. E.g. South Dakota's state epidemiologist is suggesting that reopening schools contributed to the recent increases in cases. Yay...? "It wasn't the bad decision to allow the rally that cause cases to rise, it was... uh... the bad decision to open schools!" That's just great.

They are basically speculating and guessing. Yes, I'm sure a lot were spread but that number seems grossly exaggerated.

 

[NWRatCon]

My skepticism is being assuaged. In fact, I'm now fairly confident that the study is firmly in the center of likelihood.

I have done some of my own calculations, trying not to be biased in the results, and using the expected spread based upon the average calculated R[sub]0[/sub] values (the basic reproduction number of a virus) in published materials. Those have varied between 1.4 and 4, with 2.5 being the accepted "average" for calculation purposes. Nonetheless, I chose to be conservative and used values between 1.4 and 2.75 to determine the likelihood of spread.

One of the problems of R[sub]0[/sub] is that it is not time-restricted. That is, it is the average expected number of additional infections attributed to a case (e.g., one known case = 2.5 people infected by that case). To address that, I did my calculations based upon "iterations" - the number of likely infections attributable to a case over the COURSE of the infectious period. For the "infectious period" I used the average 5-day infectious period.

Another variable that can affect the spread of a virus is the use of various methods to restrict transmission (Mask, Distance, Hygiene). This leads to an alternate R known as R[sub]e[/sub], or the "effective" R value. (Understanding R[sub]e[/sub] is important, by the way, in understanding why the EU has gotten the virus under control, and the US has not, but that is a different topic.) My assumption, given the nature of the participants in Sturgis, is that these mitigation efforts were minimal for the affected population, so I am using the basic R[sub]0[/sub] values.

The Sturgis rally occurred over the period August 7th-16th 2020. The number of out-of-state participants has been estimated at 460,000. In previous calculations I assumed 400,000. Based upon a national prevalence of .0015, I estimated that 600 participants arrived at Sturgis already infected by the disease - although with higher participation, that could reach 720, so I again used values between 600 and 720 for my calculations. Of course, not everyone infected is infectious, so I reduced that figure accordingly to 40% - 20% symptomatic, and 20% asymptomatic, but infectious. Nonetheless, it could reasonably be determined that more people left Sturgis infected than arrived that way. Local testing verifies that expectation.

Given all of that, here are my results:

At the low end: 600 infected individuals and R[sub]0[/sub] of 1.4 only 4518 cases would be attributable to Sturgis over a 30 day period.

At the high end: 720 cases @2.75 R[sub]0[/sub], there would be 311,407 cases.

That is not to say any of these calculations are "right", only that the infection RATE would be within the expected parameters over a 30-day infection period. YCMV.

 

[NWRatCon]

Here's a thorough take-down of the Sturgis study.sdThe Sturgis Biker Rally Did Not Cause 266,796 Cases of COVID-19 (Slate).

I completely understand the skepticism. I harbor it myself for the same reasons. The numbers seem too high to be plausible. But here's the thing: We'll never know. The level of testing we are conducting is insufficient to actually track the virus as it moves around the population. Another problem is being able to trace the outbreaks to particular individuals who attended the rally. The anonymized data tells us only what county they returned to, not where within that population they reside. There are so many other variables that can account for the rise in cases within those populations that making the causation inference from the correlation is problematic.

On the other hand... what is the explanation?

 

[Visbek]

On the other hand... what is the explanation?

AFAIK there are a few reasons for the increase in cases in the Midwest, mostly connected to rollbacks of restrictions, people getting tired of restrictions, and so on. Sturgis was probably only a part of it, but I concur that it is unlikely that Sturgis spread 260,000 cases.

 

[NWRatCon]

AFAIK there are a few reasons for the increase in cases in the Midwest, mostly connected to rollbacks of restrictions, people getting tired of restrictions, and so on. Sturgis was probably only a part of it, but I concur that it is unlikely that Sturgis spread 260,000 cases.

Based upon my earlier calculations and this one, I'd put the likelihood of Sturgis- related cases at between 40 and 80k cases - one or two days' worth. Not insignificant, but lower than the study asserts. It was clearly a super-spreader event as 200+ cases were directly traced to participants in the two weeks after the event. Because of our national incompetence, however, those cases will be subsumed within the general population, obscuring its impact. This polidiocy will thwart science.

 

[RAMOSS]

Thank goodness I live in Arizona.

I noticed that Arizona has gone from 10-25 new cases a day per 100K people to the 1 to 9 per day, which is showing the measures they are taking have worked.

 

[MaryP]

A study has linked 250,000 new cases of C-19 to the Sturgis event. According to Mother Jones news (which linked to the original article), a study with cell phone data links 250,000 new cases of c-19 to Sturgies.

Form Sturgis Motorcycle Rally Is Now Linked to More Than 250,000 Coronavirus Cases – Mother Jones


he inevitable fallout from last month’s Sturgis Motorcycle Rally, an annual event that packed nearly 500,000 people into a small town in South Dakota, is becoming clear, and the emerging picture is grim.

And, a link to the paper from the he Germany-based IZA Institute of Labor Economics http://ftp.iza.org/dp13670.pdf

Yes, I know Mother Jones news is rated between left and left of center, there factual basis is high. They also provided a link to their source, so the original study can be read and people can make their own conclusions based on that report. The german based institute doesn't seem to have an axe to grind in American politics,and is more interested in the economic impact.

I'm sure they're proud of themselves. But the study doesn't impress me much.

 

[RAMOSS]

I'm sure they're proud of themselves. But the study doesn't impress me much.

How special