California is monitoring 8,400 people who arrived in the state on domestic commercial flights for the Wuhan coronavirus, Governor Gavin Newsom announced on Thursday.

33 individuals have already tested positive for the virus, five of whom have been moved out of the state.

“We knew this was inevitable,” Newsom said at a press conference. State officials remain in “constant contact with federal agencies,” the governor stressed, adding that the state’s top priority was obtaining more testing kits since current supplies are “inadequate.”

“We’re not just preparing — we’ve been actively participating in addressing this issue for many months, aggressively,” Newsom said.

The announcement came after other locales in the U.S. have announced similar monitoring efforts, though none as extensive as in California. 608 people were being monitored under self-quarantine in Massachusetts, with 377 of those released without symptoms. Meanwhile, a Seattle high school announced it would close until Friday after a staffer self-quarantined following an international trip.

The CDC on Wednesday confirmed a coronavirus case in central California with unknown origins, days after the agency initially refused to test the patient because they “did not fit the existing CDC criteria.”

“At this time, the patient’s exposure is unknown,” the CDC said in a statement. “It’s possible this could be an instance of community spread of COVID-19, which would be the first time this has happened in the United States.”

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