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The coronavirus may have been silently spreading in California as early as last December — more than a month before the first US case was detected, a local official claims.

The Golden State had some of the first confirmed cases in the US including some from travelers who came from the epicenter of Wuhan, China, starting in late January.

But the deadly contagion was likely expanding way before anyone knew to look out for it, with initial cases dismissed as flu, county leaders were recently told in a briefing, according to the Los Angeles Times.

“The virus was freewheeling in our community and probably has been here for quite some time,” Dr. Jeff Smith, the chief executive of Santa Clara County government, advised them, according to the report.

Data from the Centers for Disease Control and Prevention and local health departments suggest the virus had been mushrooming “a lot longer than we first believed” — likely since “back in December,” Smith told the paper.

That is long before the first known US case — believed to be a 35-year-old Washington man in mid-January — and before local officials would have been able to test for the new virus.

“This wasn’t recognized because we were having a severe flu season,” Smith, a physician, told the L.A. paper.

“Symptoms are very much like the flu. If you got a mild case of COVID, you didn’t really notice. You didn’t even go to the doctor. The doctor maybe didn’t even do it because they presumed it was the flu.”

The theory helps explain why California started getting so many cases of so-called community spread, Smith had explained in his briefing to officials.

“That means the virus is in the community already — not, as was suspected by the CDC, as only in China and being spread from contact with China,” he said, according to the paper.