RICHMOND, Va. (AP) — Virginia Gov. Ralph Northam declared a state of emergency Thursday in response to the coronavirus pandemic, as the state’s number of confirmed cases grew to 17.

Northam advised all Virginians to avoid large gatherings “for the time being.” He said he was canceling all state conferences and large events for the next 30 days and urged local governments and private organizers to follow suit. He also announced new restrictions on travel for state workers.

“The situation is fluid, and it is changing rapidly,” Northam said at a press conference with other state officials and top lawmakers.

“Virginians should know that we have longstanding plans in place to deal with pandemics. We have trained for them and we are ready for this,” Northam said.

Virginia has 17 “presumptive positive” cases of COVID-19, the illness caused by the virus, according to the latest figures from the Department of Health.

Dr. Lilian Peake, the state epidemiologist, said at the press conference that there is so far no sign of “community spread” of the virus, meaning cases where it’s unclear how the patient acquired it.

For most people, the virus causes only mild or moderate symptoms, such as fever and cough. But for some, it can cause more severe illness, including pneumonia. The vast majority of people who contract it recover within weeks.

Thursday’s announcement from Northam came as colleges, public school districts and workplaces around the commonwealth were re-evaluating their protocols.

A cascade of Virginia colleges began announcing Wednesday that they were canceling on-campus instruction, at least temporarily. They included the University of Virginia, William & Mary, James Madison University, Virginia Commonwealth University and Longwood University, where a student tested positive for COVID-19.

Some public school districts in Virginia have announced temporary closures so that teachers can prepare for the possibility of implementing distance learning. Chesterfield County schools said they would be closed to students Friday, and Fairfax County schools were to be closed Monday.

Some large private employers, including Capital One, encouraged employees to work from home.