Washington Sen. Maria Cantwell’s office said Wednesday a D.C.-based staffer has tested positive for COVID-19. It’s the first known case on Capitol Hill.

“The individual has been in isolation since starting to have symptoms,” according to a release from Cantwell’s office. “On the advice of the Attending Physician, the senator has closed her Washington, D.C. office this week for deep cleaning and staff will be teleworking.”

The Washington Democrat’s office said Wednesday night the staffer who tested positive has “no known contact with the senator or other members of Congress.”

Cantwell has requested that other staffers who may have been in contact with the infected employee also be tested.

[Fauci: ‘Serious mitigation’ needed]

On Thursday, Sen. Tom Cotton, R-Ark., announced that he was closing his Senate office, citing an aide in another Senate office testing positive for the virus and that “other congressional employees are likely to test positive in the days ahead.”

“The most sensible course of action for the public and the congressional workforce under the circumstances is for my staff to telecommute,” Cotton said in a statement. “A weeklong congressional recess begins tomorrow, so the disruption to our in-office operations will be minimal. My D.C. office will remain closed through that recess.”

Texas Sen. Ted Cruz, who has been in self-quarantine since being notified that he had interacted with an individual who had contracted the virus, also announced that he was closing his office.

Sen. Sherrod Brown, D-Ohio, said his office has “a few more decisions to make,” and that he expects to make an announcement soon about whether he will close his D.C. office.

On the other hand, Sen. Ben Sasse, R-Neb., thinks lawmakers should stay at work on Capitol Hill next week.

“Nursing home operators in Nebraska are telling me they’re worried because they have patients who might have coronavirus, but they don’t have enough testing kits to find out,” Sasse said in a statement. “Instead of going into recess next week, the Senate ought to keep working on the people’s business — both addressing the obvious deficiencies in our diagnostic testing pipeline, and debating the President’s call last night for economic legislation. The Senate has work to do, let’s get to it.”

Lawmakers and staff have made efforts to prevent the spread of the coronavirus, or the introduction of the resulting illness, to the Capitol Hill community. The Office of the Attending Physician and other health and safety leaders have urged a regimen of disinfection and a transition to social distancing.

Washington State has become an epicenter of the COVID-19 epidemic within the U.S., and the state’s lawmakers have been especially vocal about the urgency for Congress to address the growing emergency.

The revelation came after President Donald Trump announced travel restrictions on some people coming from Europe and said he would take steps to provide financial relief for quarantined workers forced to stay home from work.

Trump said he’d allow deferred tax payments for “certain individuals and businesses” to inject a temporary infusion of $200 billion into the economy, and urged Congress to expand small business loan authority by an additional $50 billion.

The World Health Organization declared COVID-19 a pandemic Wednesday, as top U.S. public health officials warned lawmakers the virus’ spread will worsen in the coming weeks and called for aggressive mitigation.

Mary Ellen McIntire contributed to this report.