The Seattle Sounders lineup prior to taking on the Chicago Fire at CenturyLink Field on March 01, 2020 in Seattle, Washington.

Seattle-area officials announced late Thursday an employee of a 72,000-seat stadium in the city tested positive for COVID-19.

The stadium, CenturyLink Field, is home to the Seattle Seahawks, Seattle Sounders FC of Major League Soccer, and the Seattle Dragons of XFL. Local officials said the employee worked a game on Feb. 22, which 22,060 people attended, according to the Seattle Times.

"Public Health has worked with the employee and the operator of the stadium, First and Goal, to evaluate potential exposures at the Feb. 22 Seattle Dragons game," King County said in a release, "and public health officials have determined that the risk of infection to attendees was low."

Health officials are following up with a number of other employees of the stadium who might have been exposed to the virus, the county said. The county said upcoming events at the stadium will not be canceled.

The employee has not returned to the stadium since Feb. 22, First and Goal spokesman Dave Pearson said in an emailed statement, and the patient did not show symptoms while at the stadium.

"We are actively working with local and federal health agencies as well as league offices (NFL, MLS, XFL) on the latest recommendations and guidelines to ensure the safest environment possible for our guests and staff," Pearson said, adding that the stadium is rolling out "heightened sanitation procedures."

The Seattle area has become the epicenter of the COVID-19 outbreak on the West Coast of the U.S. As of Thursday, the Washington state Department of Health reported 70 confirmed cases of coronavirus in Washington, and local officials confirmed 11 deaths across the state.

As of Friday morning, there were at least 233 cases of COVID-19 in the U.S., according to Johns Hopkins University, and 14 deaths.

Most fatal cases of COVID-19 involve older people or those with underlying health conditions. King County advised people in those groups to "stay home and away from larger groups of people as much as possible."

All schools in the Northshore School District outside of Seattle closed Thursday due to the outbreak, the district announced on Wednesday. The district said all schools will remain closed for up to 14 days, and students will begin "online learning" on Monday.