(CNN)  After a US patient contracted novel coronavirus and left medical authorities no clues as to where it came from, the Centers for Disease Control and Prevention has begun sending out new testing guidance to health care workers, the top CDC official said Thursday.

A patient in California who has cornonavirus didn’t travel anywhere known to have the virus, the CDC announced Wednesday night. And the patient wasn’t exposed to anyone known to be infected.
The patient is in serious condition, Rep. John Garamendi, who represents the district in California where the patient is from, told CNN’s “OutFront with Erin Burnett.
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