Three D.C. schools—one public and two charter—said they would be closed on Monday for deep cleaning over concerns related to the spreading novel coronavirus. These are the first school closings in the region related to COVID-19, the illness caused by the coronavirus.

School Without Walls, a public high school, announced Sunday night that it would be closed because one of its staff members came into contact with a Nigerian man who stayed in D.C. for a night before developing symptoms and testing positive for COVID-19 in Maryland last week.

The D.C. Department of Health said three people who stayed with the Nigerian man were tested and came back negative for COVID-19, and the school staff member—a woman—“continues to be asymptomatic.” Still, said the school in a statement, “Out of an abundance of caution, the school will also receive a deep cleaning before students and staff return.”

D.C. International, a 6-12 public charter school with more than 1,000 students, similarly said in an email it would be closed Monday. “Late this Sunday evening we learned one of our staff members may have had exposure to the COVID-19 virus,” said the school in an email to parents. “Out of an abundance caution we will be closing school tomorrow to deep clean all surfaces and to allow for the school community to be adequately advised.”

Mundo Verde Public Charter School, whose elementary-aged students feed into D.C. International, said it would close its P Street campus: “As an act of precaution, we will close today in order to conduct a deep cleaning of our building.” The school’s campus on 8th Street NE would remain open.

D.C. recorded its first two coronavirus cases over the weekend: the Nigerian man, and Tim Cole, the rector of Christ Church in Georgetown. Mayor Muriel Bowser said on Saturday night that she would not yet declare a state of emergency in the city—as some governors have done across the country—and was urging residents to wash their hands, cover their mouths when the cough and sneeze, and stay home if they feel sick.

As of Sunday night, 18 people in D.C. have been tested for COVID-19. Fourteen of those were negative, three are pending, and one was positive. The city’s second positive, the Nigerian man, was confirmed in Maryland, but CDC guidelines will have it designated as a D.C. case.

This story first appeared on WAMU, and has additional reporting by Maureen Pao and Jacob Fenston.