The annual Sturgis Motorcycle Rally in August was widely panned by public health experts for gathering tens of thousands of people amid a pandemic.

In the months since, the impact of the rally is still being studied.

According to CDC data released in recent days, 51 attendees of the rally who resided in Minnesota were infected with the coronavirus in the days following the event. Of them, three were hospitalized and one person died.

There were also 35 coronavirus cases tied to direct contacts of those who were infected after attending the rally. Of them, one person was hospitalized.

“The findings suggest that this rally not only had a direct impact on the health of attendees, but also led to subsequent SARS-CoV-2 transmission among household, social, and workplace contacts of rally attendees upon their return to Minnesota,” the CDC said in its findings. “Whole genome sequencing results supported the finding of secondary and tertiary transmission associated with this rally.”

Amid the rally, Minnesota’s Department of Health recommended that motorcycle rally attendees quarantine for 14 days upon return and be tested 5–7 days later even if they were asymptomatic, according to the CDC.

Following the rally, the City of Sturgis required government workers to be tested for COVID-19. The city also offered testing to residents.