A fan at last week's Texans-Chiefs game at Arrowhead Stadium in Kansas City has tested positive for coronavirus, the team said on Thursday.
The Chiefs said in a statement that they had notified other fans who came in contact with the affected individual, including those in their party, using tracing "mechanisms" such as ticket data and video review.
At least 10 others who were in attendance had been asked to quarantine in addition to the fan who tested positive, KSHB reported.
The team said the other fans had been notified "within hours," in conjunction with the Kansas City Health Department, and that the fan who tested positive was limited to a single seating zone inside the stadium.
The Chiefs hosted about 17,000 fans at the opener, roughly one-fifth of their home stadium's capacity.
Meanwhile the NFL got much better news with respect to testing on both the Texans and Chiefs teams for the season-opener.
Tests revealed no positives on players, coaches and other team personnel, according to Adam Schefter of ESPN.
The tests were the first batch administered during the regular season, the report said.
However, one groundskeeper tested positive, the article said, but was not near any players.
The encouraging results for the teams was surely welcomed news for the league, which, along with the NCAA and its powerful football leagues, has been under increased scrutiny over virus safety.
The infeasibility of having bubble sites, combined with the close-contact nature of the sport, had many fearing that football teams would struggle to contain the virus, as MLB has.