The Sturgis Motorcycle Rally in the Black Hills of South Dakota has returned despite last year’s rally being derided as a superspreader event.

This year’s event started on Friday amid a rise in Covid-19 cases as the Delta variant of the virus spreads rapidly among the unvaccinated. The state health department reported a 68 per cent rise in infections in South Dakota last week.

Sturgis organisers expect more than 700.000 people to attend during the 10-day event. Only about 46 per cent of adults who live in the county that hosts Sturgis are fully vaccinated, according to the Centers for Disease Control and Prevention, compared with 60.6 per cent nationwide.

Around 7.000 people live in Sturgis in western South Dakota, but the town is transformed into a huge motorcycle hub around this time each year, after being held for the first time in 1938.

A review of cellphone data found that more than half of the counties in the US were visited by someone who attended Sturgis during last year’s event. Hundreds of rally-goers were infected, and a team of researchers from the Centers for Disease Control found that the rally resembled a “superspreader event”.

The event is expected to be even bigger this year, and few wear masks.

“We’re out in the wide-open,” one rally-goer told the AP. “If you want to wear a mask, that’s your business. If you don’t, that’s your business.”

“A lot of that, I don’t worry too much about,” JJ Vilella said about the pandemic. He’s unvaccinated. “If it happens, it happens.”

“Living in Sturgis, I do hear [of] people that live here that don’t love the rally,” Sturgis emergency-room nurse manager Rikki Plaggemeyer, 46, told The Daily Beast. “If you don’t like to live in Sturgis, and you don’t like the Sturgis Rally, you shouldn’t live here. It gives us great experiences in the ER and in the hospital, and I spend most of my time during the rally here.”

“We generally can talk them into wearing” a mask Ms Plaggemeyer said of Sturgis attendees who end up in the hospital. Some have been told that the hospital could refuse to treat them if they didn’t put on a face covering. “Most of the time they will comply. I don’t think we’ve ever had issues of people not getting treatment because of it.”

Registered nurse Jamie Lascelles, 30, told the outlet: “We do have some that don’t approve of it. And it’s unfortunate, but that’s just kind of where we live.”

The vice president of medical affairs at Monument Health in Rapid City south of Sturgis, Dr Shankar Kurra, told The Daily Beast that there’s a “very high risk” that many will be infected during the rally.

“My concern would be with the Delta variant, which as we know is highly transmissible,” the 54-year-old said. “The fact is, it’s a mass gathering event. It puts people at risk. That’s the nature of this virus.”

Dr Halie Anderson, an allergist and immunologist in Rapid City, said “the rally has a lot of benefits for the area, and it benefits the economy. But I think this has the potential to do a lot of harm”.

Marketing firm owner and Rapid City resident Natalie Slack told The Daily Beast: “I think the big concern is that this is a gathering of mostly anti-vaxxers or people who are so intent on celebrating freedom that they sometimes neglect the care and concern for the community they’re visiting/invading.

“I feel some level of safety in the vaccine — in knowing that even IF we get sick, we likely won’t get as ill as we may have otherwise.”

She said she was concerned for her 65-year-old parents who are being treated for cancer.

“My concern is primarily for them as they navigate how to be and where to go through this mayhem,” she said.

Five people died during last year’s rally, four of whom passed following vehicle crashes. But many times in the past, more than 10 people have died.

“Unless it’s a member of your family or social circle, locals might pause for a ‘too bad’ moment, but otherwise it’s just another biker,” retired journalist David Super, 74, told The Daily Beast. “In years past, where there were more violent or drug-related deaths, then locals would spend a few more moments, but we don’t dwell on the topic.”

“The Sturgis rally is about hopping on your bike and exploring this great country through our open roads,” South Dakota Governor Kristi Noem tweeted on Wednesday. “Bikers come here because they WANT to be here. And we love to see them! There’s a risk associated with everything that we do in life. Bikers get that better than anyone.”

“I’m going to go every year until I die, whether Covid kills me or a head-on collision,” Steve Sample, 67, a land surveyor from Arizona, told CNN. “That’s the way I am.”

The owner of the Sturgis Buffalo Chip campground Rod Woodruff told the outlet: “People come here because they’re free of all that unnecessary political government control exercised over their lives.”

“All these people here... know all the crap, all the baloney that has gone back and forth about how dangerous all this unseen stuff is and the viruses,” he added. “Everybody’s aware of all that and they have assumed the risk of getting out of their home and getting away and going someplace else and hanging out with people that are like-minded.”

The Associated Press contributed to this report