More than two dozen Colorado school districts that collectively serve more than two-thirds of the state’s students announced Thursday that they would close for several weeks in an attempt to slow the spread of the new coronavirus.

Denver Public Schools, the state’s largest district with 93,000 students, joins other large districts in the Denver metro area and in the Colorado Springs region in the decision. All are closing for between two and three weeks, with some effectively extending their spring breaks and others transitioning to online learning.

Among the districts: Jeffco Public Schools, with 84,000 students; the Douglas County School District, with 67,000; the Cherry Creek School District, with 56,000; Aurora Public Schools, with 40,000; Adams 12 Five Star Schools, with 38,700 students; the St. Vrain Valley School District, with 32,900; the Boulder Valley School District, with 31,000; School District 27J in Brighton, with 19,000; and Littleton Public Schools, which serves 15,000 students.

The Gunnison Watershed School District in Colorado’s High Country also closed, the first district in the state to do so.

William Burman, an infectious disease specialist with Denver Health, said at a press conference with Denver Public Schools officials on Thursday that there is now evidence of community transmission of COVID-19. Public health officials hope that closing schools will slow the spread by reducing the amount of contact people have with each other. For that reason, Denver Public Schools won’t offer child care during the extended closure.

As of Thursday evening, there are no known cases among Denver students or staff of COVID-19, the disease caused by the new coronavirus.

Denver schools will be open for learning as usual Friday. The schools will also be open on Monday and Tuesday for students to gather their belongings, but no teaching will take place. After that, the schools will be completely closed until Monday, April 6, which was an already scheduled teacher work day. Students are expected to return on Tuesday, April 7.

District officials acknowledged this is a time of disruption and uncertainty.

“This is the time to lean in to the DPS family spirit,” said school board Vice President Jennifer Bacon.

The news comes just one day after state public health officials issued much more limited school closure guidelines, and two days after Gov. Jared Polis declared a state of emergency. On Thursday, the city of Denver also declared a state of emergency. The day brought a string of regional and statewide school closures around the country, including Seattle, Indianapolis, and Memphis schools, as well as Ohio and Maryland. At the same time, New York and Chicago schools remained open, even as students in both cities were diagnosed as positive for COVID-19.

Other Colorado districts remain open for now. The diversity of decisions reflects Colorado’s principle of local control. Unlike governors in other states, Polis has not ordered any schools to close. Even as the Gunnison district decided to close, schools in Eagle and Pitkin counties remain open, even though they have more cases.

As of Thursday afternoon, there were 49 cases of COVID-19 in Colorado, which include an “indeterminate” case that state officials are treating as positive. State public health officials acknowledged that testing capacity has not kept pace with demand.

The 49 cases include 11 in Eagle County; 10 each in Pitkin County and Denver; four in Jefferson County; three each in Arapahoe, Douglas, and Gunnison counties; two in Adams County; and one each in Larimer, El Paso, and Summit counties.

At least four cases involve family members of Denver public school students. A fifth case involves a parent of a student at the private St. Anne’s Episcopal School in Denver.

St. Anne’s was the first school to close last week in response to the new coronavirus. That was followed by three Denver public schools this week: Cory Elementary on Wednesday, and Edison Elementary and John H. Amesse Elementary on Thursday.

Denver Public Schools Superintendent Susana Cordova said the district does not expect at this point to offer online classes while schools are closed. The district will offer free meals to students at eight locations throughout the city, using a “grab-and-go” style system to prevent large groups from gathering.

The eight locations are: Abraham Lincoln High School, Joe Shoemaker School, Place Bridge Academy, Denver Center for International Studies Baker, North High School, Manual High School, the Montbello campus, and the Evie Dennis campus.

Denver’s decision to not offer online learning stood in contrast to Jeffco Public Schools, the state’s second largest district. Jeffco’s announcement said that starting Monday, “our school buildings will be closed for in-person classes. … students will learn from home.”

There have been no confirmed cases of the virus in Aurora schools. Thursday was the last scheduled day for most Aurora students before spring break. Friday was a district teacher planning day, and spring break was to start Monday. Now instead of returning to classes March 23, Aurora students and staff will be out of school through March 27.

Aurora will reassess and decide “whether students and staff should return March 30.”

The district is also cancelling all athletics, activities, events and childcare during that time. The announcement notes that the district will be asking the state for flexibility from mandatory seat time and state testing requirements.

Aurora’s Thursday notice also said there will be follow-up communications “with additional information about distribution of meals, access to online education resources and new developments.”

Colorado obtained a waiver from the federal government to allow districts like Aurora and Denver to make food available at “grab-and-go” locations. Federal school lunch rules typically require children to eat those meals at school.

State rules, which remain in effect for districts holding class, state that any school or child care center with a confirmed case in a student or staff member must close for at least 72 hours for cleaning. A second case within 30 days would require another 72-hour closure. Any school with three or more confirmed cases within 30 days will have to close for at least 14 days.

And if three schools in a district have confirmed cases within 30 days, all schools in the district would have to close for at least 14 days for cleaning, testing, and public health investigation.

Chalkbeat bureau chief Erica Meltzer contributed to this report.