Coronavirus: Almost 20% of cases in past month stem from controversial motorcycle rally, research claims

A motorcycle rally held in South Dakota in August and attended by hundreds of thousands of Americans from across the country is linked to more than 260,000 Covid-19 cases recorded in the US since 2 August, a new study suggests, with researchers describing the event as a "worst-case scenario" for spreading the disease.

Between 7 and 16 August, around 450,000 people from across the states flocked to Sturgis for the annual 10-day Sturgis Motorcycle Rally, which featured several concerts and was held despite cases soaring across the country. Last week, a 60-year-old man with underlying health conditions was the first known person thought to have died with coronavirus having attended the event.

The study, by San Diego State University's Center for Health Economics & Policy Studies, estimates that the 260,000 figure represents around 19 per cent of all virus infections reported in the US between 2 August and 2 September.

As part of their study, the reserchers tracked anonymised mobile phone data that showed “smartphone pings from non-residents” and “foot traffic at restaurants and bars, retail establishments, entertainment venues, hotels and campgrounds each rose substantially.”

Using that data and linking it to corresponding rises in Covid-19 cases, the researchers - aided by a team of economists - calculated that the public health cost associated with treating the infections was in the region of $12.2 billion (£11.1bn). "This is enough to have paid each of the estimated 462,182 rally attendees $26,553.64 not to attend," the researchers claim.

It is understood that the annual festival, which went ahead with the blessing of South Dakota governor, Kristi Noem - an ardent Donald Trump supporter - generates somewhere in the region of $800 (£618) million in revenue. Festival attendees did not wear face coverings or practise social distancing while at the event, The Associated Press reported at the time.

“The Sturgis Motorcycle Rally represents a situation where many of the ‘worst-case scenarios’ for superspreading occurred simultaneously: the event was prolonged, included individuals packed closely together, involved a large out-of-town population (a population that was orders of magnitude larger than the local population), and had low compliance with recommended infection countermeasures such as the use of masks,” the researcher wrote in the paper, which is awaiting peer review.

An estimated 62,182 vehicles entered Sturgis over the 10-day period the festival took place - a 7.5 per cent decrease from 2019, according to the South Dakota Department of Transportation. According to data gathered by the researchers, some 90 per cent of the rally’s attendees travelled to Sturgis from out of state, with the majority coming from the south and midwest of the US.

Governor Noem criticised the study, branding it "fiction" as she attacked journalist for reporting on its findings. “This report isn’t science; it’s fiction. Under the guise of academic research, this report is nothing short of an attack on those who exercised their personal freedom to attend Sturgis,” Noem said in a statement on Tuesday. “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."

South Dakota health officials also questioned the study's findings. "The results do not align with what we know for the impacts of the rally," state epidemiologist Josh Clayton said on Tuesday.   The number of cases reported in the study differs dramatically from the number of cases reported by state health chiefs.  As of Tuesday, the state had reported 124 cases among South Dakota residents who got ill after attending the event. The Associated Press as of last week identified 290 cases from 12 states tied to the rally.

South Dakota Secretary of Health Kim Malsam-Rysdon cast doubt on the methodolgy used in the paper. "I would just caution you about putting too much stock into models ... that can't be verified by other factual numbers," Malsam-Rysdon said in reference to the study. "I think that is the case with that particular white paper."

But Andrew Friedson, one of four authors of the study, defended the study's findings. "We're never going to be able to contact trace every single person from Sturgis," he told USA Today. "So if we want a good-faith estimate using, at the moment, the accepted statistical techniques ... this is the best number we're going to get in my opinion."