A staffer in Sen. Maria Cantwell’s D.C. office has tested positive for the coronavirus, the Washington state Democratic senator announced on Wednesday night.

The announcement marks the first known instance of a congressional staffer getting the virus and follows days of heightened anxiety on Capitol Hill.

The staffer, according to a notice from Cantwell’s office, has been isolated since they started to have symptoms. Cantwell is closing her D.C. office for the remainder of the week for a deep cleaning.

“The individual who tested positive for COVID-19 has had no known contact with the senator or other members of Congress. The senator is requesting that testing be done on any other staffers who have been in contact with the individual and show symptoms,” the notice continues.