Saw an update on this today.
Within weeks of the gathering that drew nearly half a million bikers, the Dakotas, along with Wyoming, Minnesota and Montana, were leading the nation in new coronavirus infections per capita.
Long and informative article. The link is through MSN, so maybe not paywalled.
I hadn’t realized this (my bold):
But this year, a survey found that 60 percent of residents wanted the rally postponed. At council meetings, people lined up to argue. A nurse warned there wouldn’t be enough hospital beds if the event went forward, while a business owner said she would lose her building if it didn’t. Calling off this year’s rally, its 80th anniversary, would mean a loss of around $2 million for the city, authorities said. It had only been done during World War II.
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In the run-up to the rally, officials estimated that 250,000 people would come. The actual number, according to the South Dakota Transportation Department, was over 460,000 — down just 7 percent from 2019.
They came in the greatest numbers from South Dakota, source of an estimated 93,000 attendees, or a fifth of the total, according to calculations by the Center for New Data. Minnesota ranked second, with an estimated 31,000 people, followed by Colorado with 29,000. Many traveled hundreds of miles: 21,000 rallygoers are believed to have come from Texas, and 20,800 from California.
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“No one that I spoke to there wasn’t aware of coronavirus, and wasn’t aware that there was a risk of them being there,” Crerar said. “It was just a risk that they accepted.”
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A “risk they accepted” on behalf of OTHER PEOPLE who had no say in the matter. 
This guy Cervantes is identified at the beginning of the article as someone who went to the rally against his girlfriend’s advice. He got very sick, spent a week in the hospital. At least at the end he acquired some wisdom.
Cervantes now looks at things differently. Watching football, he worried how many of the thousands of fans admitted to a recent Kansas City Chiefs game might become infected, even as he noticed they sat apart. He once put on a mask to humor Balcom [his girlfriend]; now he says he has to resist the urge to yell at strangers to wear them.
After weeks of missed work, his stint in the hospital and a return visit to the ER over a blood clot concern, he’s come to deeply regret his decision.
“I was naive,” he said. “I was dumb, you know? I shouldn’t have went. I did; I can’t change that, so I just got to move forward. But sitting here just the past few days, that’s all I keep thinking about. I’m like, Jesus, look at the hell I’m going through, the hell I put everybody through. It ain’t worth it. It wasn’t. It really wasn’t.”
He’s lucky he lived to regret the decision.