The Orange County Health Care Agency's Communicable Disease Control Division, which received confirmation from the Centers for Disease Control and Prevention, said the infected person is a traveler from Wuhan, China.
The respiratory disease has sickened 1,975 people and killed 56, almost all in Wuhan.
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The patient was transported to a local hospital and is isolated in good condition, according to officials.
Health officials said there was no evidence that person-to-person transmission has occurred in the county, and that the current risk of local transmission remains low.
It was not immediately clear where and how the traveler entered into the country or county.
A passenger who landed at Los Angeles International Airport Wednesday night was hospitalized for a precautionary medical evaluation amid increased concerns over the viral infection.
Children's Hospital Los Angeles confirmed a patient who has a common strain of coronavirus was being treated. Hospital officials say children with four different types of coronavirus are treated on a regular basis, including the patient who was recently admitted.
Canada, Australia and Malaysia reported their first cases Saturday and Japan, its third. France confirmed three cases Friday, the first in Europe, and the U.S. identified its second, a woman in Chicago who had returned from China.
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