D.C. Mayor Muriel E. Bowser declared a state of emergency Wednesday that allows her to enforce quarantines and cancellations to slow the spread of the coronavirus, as major churches and organizations in and around the nation’s capital said they would shut down for the rest of the month.

The Episcopal Dioceses of Washington and Virginia said churches including Washington National Cathedral would close for two weeks. The Walter E. Washington Convention Center canceled upcoming events, as did the promoter of concerts at the Anthem, the 9:30 Club, the Lincoln Theater and U Street Music Hall.

Organizers said parts of the annual Cherry Blossom Festival would be shelved, the Rock ‘n’ Roll Marathon had its city permit pulled, and the St. Patrick’s Day parade scheduled for Sunday was postponed indefinitely.

As the coronavirus continues to spread, phrases like “quarantine,” “isolation” and “social distancing” are making news. Here are the key differences of each. (The Washington Post)

More colleges and schools announced plans to close for deep cleaning or move to online classes.

Bowser announced six new coronavirus cases, including two not linked to any known source of infection, bringing the total number of confirmed cases in the District, Maryland and Virginia to at least 34. Officials in Alexandria, Va., announced the first case there late Wednesday.

Bowser said the District has leased an undisclosed location that can be used to quarantine up to 50 people.

“I want to continue to remind everyone to be vigilant,” Bowser said at a news conference. “Our duty now as citizens is to try to contain the spread of germs and this virus in our communities.”

Before the emergency declaration, the owner of the Washington Wizards and the Washington Capitals said their games would go on as scheduled at Capital One Arena in the District’s Chinatown neighborhood.

Later, the National Basketball Association announced that it would suspend its season indefinitely after a Utah Jazz player tested positive for the virus.

City health officials earlier Wednesday had recommended canceling all “non-essential mass gatherings” of 1,000 people or more through the end of the month.

Health officials also expanded a self-quarantine recommendation for people who have visited Christ Church Georgetown, which is now linked to three confirmed coronavirus cases.

Rev. Timothy Cole, 59, the church rector, was diagnosed with the virus after attending an Episcopal leaders conference in Louisville. Organizers of the conference said Wednesday that two other conference attendees have also tested positive.

In recent days, Christ Church organist Tom Smith and a church member from Loudoun County also were diagnosed with the virus.

After Cole’s diagnosis, city officials urged people who had been at the church on Feb. 24 or between Feb. 28 and March 3 — days when Cole was there — to quarantine at home and monitor themselves for symptoms.

But the city has since extended the recommendation to include people at the church March 4 through March 6, to account for the days Smith was there. Smith played at a funeral on March 6, and those who attended that service are also being alerted, the church said in an email to members. City officials want people to stay isolated until two weeks have passed since their last time at the church.

Authorities say anyone who develops symptoms, such as a fever, cough or shortness of breath, and believes they have been exposed to the virus, should consult their health-care provider about whether to be tested.

Health-care experts say that those who are sick should stay home and that everyone should wash their hands thoroughly and regularly, or use alcohol-based hand sanitizer. Those with compromised immune systems are also advised to take precautions.

The six new coronavirus cases in the District include a 59-year-old man and a 39-year-old man who traveled abroad; a 58-year-old woman who attended a conference where other participants tested positive; and a 59-year-old woman who came in contact with another person who previously tested positive in the District. Officials said they have not identified a probable source of exposure for the other two people, a man in his early 20s and a 69-year-old woman.

Such cases — when there is no obvious likely origin — are the most concerning to health officials and are a primary reason for considering widespread closures and disruptions, officials say. The goal is to limit the spread of the virus by patients who have not yet been diagnosed and quarantined.

“We have person-to-person transmission occurring in the District of Columbia, as well as at least two individuals whose reasons for covid-19 have yet to be identified,” D.C. Health Director LaQuandra S. Nesbitt said at the news conference where Bowser announced the state of emergency.

Alexandria officials said a resident who tested positive for the coronavirus had been in contact with a District resident with the virus who was associated with Christ Church and had spent time at the Immanuel Chapel of the Virginia Theological Seminary, according to a news release. The age and gender of the person was not immediately available.

Earlier in the day, Virginia Gov. Ralph Northam (D) on Wednesday reported on another new coronavirus case in his state: a male teenager in the Chickahominy Health District, in the area of Hanover County.

The teen, who does not attend school, visited a country where there is “ongoing transmission” of the virus, said Caitlin Hodge, a spokeswoman for the health district. He returned from his trip on March 4, started having symptoms on March 8 and was tested.

Northam said steps were being taken in several agencies — including schools, transportation and health — to make sure the commonwealth is prepared to deal with the virus. He has not yet declared a state of emergency but said he is “prepared to do so.”

The state’s public lab has testing supplies for 300 to 400 patients, and it anticipates receiving additional tests soon to increase that capacity to 600. Until testing capacity increases, health department officials will give priority to people who have had contact with others with confirmed cases, who have traveled to impacted areas and who live in nursing homes.

Daniel Carey, Virginia’s secretary of health and human resources, said that given the limited number of tests available, it makes sense for doctors to first test patients for flu, pneumonia or bacterial infections to rule out those conditions.

In Maryland, Gov. Larry Hogan (R) announced four new cases: a woman in her 70s who tested positive in Anne Arundel County after having close contact with someone else who had the virus; a Montgomery County man in his 20s who recently traveled to Spain; a Baltimore County man in his 60s who was at the American Israel Public Affairs Committee policy conference in the District; and a Prince George’s County man in his 60s, who is currently hospitalized. That man’s travel is being investigated.

The governor told residents to brace for social-distancing measures and warned of “significant disruption to your daily lives for a period of time.” He urged local governments to consider canceling large events, ordered nursing homes to bar nonessential visits, curtailed walk-in visits to the Motor Vehicle Administration and instructed local schools and preschools “to be prepared with contingency plans for potential long-term closures.”

State businesses will have an automatic extension on state tax filings, until June 1, Maryland Comptroller Peter Franchot said.

The Internal Revenue Service deadline of April 15 for income and corporate taxes remains unchanged.

Events D.C., the District’s tourism arm, said Wednesday that officials have learned of two other AIPAC attendees — from Ohio and Toronto — in addition to three cases announced earlier.

Officials say there was a low risk of exposure for people who attended the conference, because the patients did not show symptoms during the conference, said Gregory A. O’Dell, president and chief executive of Events D.C.

Indoor venues managed by Events D.C. — including the convention center, the D.C. Armory, and the R.I.S.E. Demonstration Center — will undergo a deep cleaning in coming days, he said, “out of an abundance of caution.”

He said the suspension of operations at the convention center and other facilities will affect three Capital City Go-Go basketball games, a circus and the finish line and expo associated with the Rock ‘n’ Roll Marathon.

The decision to shut down immediately affected Satellite 2020, an annual technology convention that has been held in the District for 39 years. The convention started Monday, was scheduled to end Thursday, and was expected to draw more than 15,000 attendees from more than 100 countries, organizers said.

Pete Schramm, a sales engineer based in Maryland, said the mood at the convention was “subdued” Wednesday over concerns about the coronavirus.

“Nobody wants to touch you and people are keeping their distance,” he said while having a cigarette outside the convention center. “People are very reserved, they’re quiet and they seem to have a lot on their minds.”

Restaurateurs such as Jamie Leeds, the chef-owner of Hank’s Oyster Bar, were bracing for a significant drop in customers, especially in neighborhoods anchored by large event spaces.

“The Anthem is a huge driver of business for us,” said Leeds, referring to the huge new concert venue in Southwest Washington that has canceled all events until April 1.

But Leeds, who has three other locations in the D.C. area, said the restaurant is also a neighborhood destination with many regulars.

Leeds said she supports the Anthem’s decision to cancel events. “It’s important to follow the guidance of the city and what’s best for people’s safety,” she said.

Laura Vozzella in Richmond and Erin Cox, Fritz Hahn, Marissa J. Lang, Luz Lazo, Justin Wm. Moyer and Ovetta Wiggins contributed to this report.