Only two NFL teams opened their stadiums to fans in Week 1.

A fan at one has since tested positive for COVID-19.

The Kansas City Health Department announced Thursday that an individual who attended the Chiefs game last Thursday at Arrowhead Stadium has tested positive for the virus. Ten people who were in close contact with the person have been identified and are under quarantine.

“The contact tracing mechanisms that the club has in place, including parking and ticket scanning data, as well as video record review, indicate that the individual’s party entered the stadium in compliance with mask mandates,” the Chiefs said in a statement. “Within hours of being notified, the Chiefs were able to pinpoint the names of the other members of the party as well as detailed information about the path and location of entry, and this information was provided to the Health Department.”

The team said the infected individual and its group were seated in the lower level of the stadium. All staff members who interacted with the person were required to wear personal protective equipment, including a mask.

The Chiefs opened their stadium at 22 percent capacity — the announced attendance was 15,895 — for the NFL’s season opener. All were required to wear masks when they were not eating or drinking.

All tests of players, coaches and team employees from the Chiefs and Texans came back negative this week, ESPN reported. A groundskeeper at Arrowhead Stadium did test positive, but he was not near the players, according to the report.

The Jaguars were the other team to have fans in attendance for Week 1, but the Browns, Dolphins, Colts and Cowboys are expected to have a limited amount in Week 2.

“I want to remind everyone that COVID-19 is anywhere and everywhere,” Kansas City health director Dr. Rex Archer said. “While we’re all tired of it, frustrated and even angry at how it has altered and stricken our lives and livelihoods, we must continue to think of those who have not and will not survive it.”