WASHINGTON (AP) — Washington health officials recommended on Wednesday that all "non-essential mass gatherings, including conferences and conventions," be postponed or canceled through the end of March in light of the coronavirus outbreak, a move that could imperil the popular Cherry Blossom Festival.

The announcement signals a major escalation in the District of Columbia's response to the spread of the virus.

A brief statement from the District of Columbia Health Department did not mention the Cherry Blossom Festival, but it recommended that "any social, cultural, or entertainment events where large crowds are anticipated be reconsidered by the organizer" through March 31. It defined mass gatherings as "events where 1,000 or more people congregate in a specific location."

Officials have steadfastly refused to speculate on the fate of the Cherry Blossom Festival, which starts on March 20 and typically signals the beginning of Washington's tourist high season.

Washington officials declined to comment beyond the statement, but Democratic Mayor Muriel Bowser scheduled a briefing for later in the afternoon.

The announcement has massive implications for Washington's many museums, events and performance venues. The city's St. Patrick's Day parade has been postponed, and Eileen Andrews, a spokeswoman for the Kennedy Center for the Performing Arts, said they were "in the process of assessing what the Mayor's recommendation means for the Kennedy Center."

Lauren Lyons, a spokeswoman for the Smithsonian network of museums, said in an email: "As of now the Smithsonian is continuing to welcome guests to our museums and scheduled public programs as normal."

Events DC, which operates the Walter E. Washington Convention Center, said five people who attended the recent AIPAC conference there had tested positive for the coronavirus, up from the two that AIPAC had publicly reported. As a result, Events DC said it was suspending operations from March 13 to March 31 "out of an abundance of caution." The convention center is hosting a large convention for the satellite industry, which is scheduled to end Thursday.

Also Wednesday, Georgetown University joined the growing list of higher learning institutions to cancel in-person classes as fears of infection by the COVID-19 coronavirus continue to progressively warp daily life from coast to coast.

A statement on the Georgetown website announced that the university is "suspending all in-person, on-campus classroom instruction" until further notice and would be "moving all classroom instruction for all of our schools to virtual learning environments."

The announcement came a day after American University in Washington made a similar move. As with American University, the Georgetown dorms will remain open, but students are encouraged to return home instead of staying on campus. Dozens of universities, including UCLA, Duke, Ohio State, Harvard and Purdue have done the same.

Georgetown has reported no suspected cases of coronavirus infections on campus. However, the university hospital is treating Washington, D.C.'s, first identified victim.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia.

The vast majority of people recover from the new virus. According to the World Health Organization, people with mild illness recover in about two weeks, while those with more severe illness may take three to six weeks to recover.

In Washington, the Rev. Tim Cole, rector of Christ Church Georgetown Episcopal church, has identified himself as the city's first patient. City officials asked several hundred people who entered the church on days when Cole was present and symptomatic to quarantine themselves. Two subsequent positive infection cases, one living in Washington and the other in Virginia, have been Christ Church parishioners. The church has canceled all services and activities indefinitely.

Cole released an open letter to his parishioners on Tuesday, saying he was improving slowly and describing his illness as "a strange up-and-down experience." He apologized for the disruption in his parishioners' daily lives but said it was necessary.

"Being the first point of outbreak in Washington obviously required strong measures, but I fully understand the inconvenience, and I deeply apologize," Cole wrote.

The District of Columbia has reported four positive virus cases, although that number doesn't include people who may have been infected in Washington but live in nearby northern Virginia or southern Maryland. For example, Loudoun County, Virginia, has reported a positive case in a local resident who is a Christ Church congregant.

Some Washington schools have closed for one day to enable deep cleaning. The district's public school system on Wednesday announced it would move a planned professional development day for teachers and staff from March 20 up to Monday to focus the day on virus-related training and preparation.

About a half-dozen members of Congress are on a 14-day self-quarantine after coming in contact with potentially infected people. On Tuesday, Virginia Democratic Rep. Don Beyer announced he would self-quarantine after dining 10 days ago with a person who tested positive for the virus.

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