Outbreaks can be seeded when people cluster in bars, such as this one in Sturgis, S.D., during the Sturgis Motorcycle Rally in August.

STURGIS, SD – AUGUST 09: People watch a concert at the Full Throttle Saloon during the 80th Annual Sturgis Motorcycle Rally in Sturgis, South Dakota on August 9, 2020. While the rally usually attracts around 500,000 people, officials estimate that more than 250,000 people may still show up to this year’s festival despite the coronavirus pandemic. (Photo by Michael Ciaglo/Getty Images)