Facebook on Thursday confirmed that a contractor at a Seattle office had been diagnosed with coronavirus and the social media giant said it would close that location until March 9.

“A contractor based in our Stadium East office has been diagnosed with the COVID-19,” a spokeswoman said in an emailed statement.

Facebook said it had notified employees, adding that workers in all Seattle locations were being encouraged to work from home until the end of the month.

Seattle in Washington state has the largest concentration of coronavirus cases confirmed to date in the United States.