State health officials reported six new presumed cases of coronavirus Thursday in New Jersey, bringing the statewide total to 29, and prompting Gov. Phil Murphy to urge that large public gatherings in the state be canceled for now.

In Bergen County, which has seen the largest outbreak of COVID-19 cases, County Executive Jim Tedesco said Thursday night that he decided to close schools in all 75 of the county's school districts at 3 p.m. Friday and have them transition to online learning in an effort to curb the spread of the coronavirus.

The decision came as Bergen County saw its presumed cases of coronavirus, or COVID-19, rise by two Thursday to 13, the most of any county in the state. The risk to residents in the county was described as "moderate" by state health officials.

Tedesco said a decision to close schools was "a paramount decision and I don't take it or make it lightly."

The county's 75 districts include 170,000 students, 16,000 teachers and hundreds of administrators. There are now cases in 11 of the state's 21 counties.

The "steep increase" in cases statewide — from one to 29 in a week — motivated officials "to step back and say, 'What further mitigation strategies should we undertake,' " said state Health Commissioner Judith Persichilli.

Based on her recommendation, Murphy urged that all gatherings of more than 250 people be canceled, including parades, concerts and sporting events.

"Social distancing works," Murphy tweeted. "This is our best chance to mitigate the chance of exposure & rapid spread of #COVID19."

Tedesco met with school district administrators Thursday.

"We are confident in the ability of Bergen’s teachers, staff and administrators to take action as necessary,” he said.

Already, districts including the Bergen County Technical Schools and East Hanover in Morris County have closed because of coronavirus concerns. And more than 180 districts closed for a day or an afternoon to clean or instruct teachers on remote learning training this week, according to Lamont Repollet, the state education commissioner.

Among the patients who received "presumptive positive" diagnoses of coronavirus Thursday was the youngest person to test positive so far in New Jersey, a 16-year-old Englewood girl who is being treated at Englewood Health hospital. The others are:

a 66-year-old Montclair woman, being treated at Hackensack Meridian Health Mountainside Medical Center

a 51-year-old Butler man, who is a patient at Chilton Medical Center in Pequannock

a 23-year-old Bridgewater man, in Somerset County

a 53-year-old Manalapan man, in Monmouth County

a Teaneck woman whose age was not available.

Those include the first cases from Essex, Morris and Somerset counties. There are now cases in 11 of the state's 21 counties.

Montclair State University sent a letter to students and staff saying the university learned Thursday that a member of the campus community was diagnosed with COVID-19. "The patient is an employee who was last on campus on Friday, February 28, 13 days ago," wrote Patricia Ruiz, director of the university's health center. "The individual did not have symptoms of COVID-19 when they left the office, so it is believed that the risk of exposure to other members of the campus community is low."

Montclair State students have been on spring break this week, and the university said it will extend break through March 22. Starting March 23, the majority of instruction will take place online for the rest of the semester.

"The University is open and campus facilities and services are functioning as they would have been without the coronavirus, except for events and large gatherings being canceled," said university spokeswoman Erika Bleiberg.

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The Health Department has begun classifying the level of risk for each county in a new COVID-19 "dashboard" on its website. Bergen County's risk is ranked as moderate, while the risk in Monmouth County, with five cases, is "above minimal, but below moderate," Persichilli said. For the rest of the counties, the risk is ranked as "none or minimal."

So far, two of those diagnosed in New Jersey have been health care workers, Persichilli said, emphasizing that their protection is "so important," because they can expose an entire team of coworkers whose need for quarantine would disrupt the health care system.

New Jersey has successfully sought the release of additional personal protective equipment for health care workers from the federal stockpile of emergency supplies, said Chris Neuwirth, an assistant commissioner of health who testified before a Congressional subcommittee on Tuesday. "We're actively moving forward with procuring supplies from the strategic national stockpile," he said Thursday.

The state is also in the process of testing 37 potential cases at the state public health laboratory. An unknown number of other samples may be being tested by commercial laboratories, Persichill said. In addition, Hackensack Meridian Health began use of a rapid-results test for patients hospitalized in its system Thursday.

Patrick Callahan, superintendent of the New Jersey State Police, said his agency has the power to stop events if the state believes there is a public health threat. "We do reserve the right to come in and go, 'You're not having that event, you're not having that wrestling match, basketball game, concert,' " Callahan said.

Legislative leaders in Trenton have been discussing how to respond to the coronavirus outbreak and whether to adjust schedules. On Thursday afternoon, most Assembly committee meetings planned for Monday in Trenton were canceled.

And Chief Justice Stuart Rabner announced New Jersey courts will suspend all new jury trials until further notice to help minimize community exposure to COVID-19 coronavirus.

In Bergen County, there are now five cases in Teaneck; four cases in Englewood; two cases in Bergenfield; one Fort Lee case; and one Little Ferry case, a patient who earlier this week had become the first New Jersey resident to die from coronavirus.

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State officials had reported on Wednesday the first signs that the illness may be spreading broadly in the community, noting that two of the most recent patients to be identified had no connections to any known sources of exposure.

With health officials at all levels of government asking people to practice social distancing to keep the virus from spreading, many organizations have canceled events, from professional and college basketball and soccer games to upcoming St. Patrick's Day parades. On Thursday, Major League Baseball suspended spring training and the NCAA canceled postseason basketball tournaments.

The 2020 Montclair Film Festival and the Montclair Literary Festival have been postponed, according to officials of both organizations.

The rabbinical council of Bergen County on Thursday said that all of its synagogues will be closed for the coming week, which means there will be no prayer services. In addition, kosher restaurants will be take-out only, and the council said that no large social gatherings should be held.

SAT testing scheduled for this weekend at Ridgewood High School has been canceled, the district said.

In New York, Broadway theaters are going dark. New York Gov. Andrew Cuomo on Thursday announced a ban on gatherings of more than 500 people. Broadway is shuttered at least until April 12, according to The Broadway League.

The focus on the virus has led some people to stock up heavily on food and sanitary products, and companies are putting limits on how much of those items a customer can buy at a time.

The World Health Organization on Wednesday declared the coronavirus outbreak a pandemic, as the global death toll rose above 4,300 and the number of confirmed cases exceeded 120,000.

“My guess is it gets worse before it gets better," Murphy said in an interview Wednesday. "And that’s not just a statement about New Jersey. That’s a statement about America and the world. We have been preparing for that, and we just have to continue to do what we can to stay out ahead of that.”

Reporters Ashkey Balcerzak, Stacey Barchenger, John McAlpin and Terrence McDonald contributed to this story.

Check back for updates on this developing story.