Though C.D.C. officials said it was possible the patient was exposed to a returning traveler who was infected, the new case appears to be one of community spread - one in which the source of infection is unknown.
"That would suggest there are other undetected cases out there, and we have already started some low-grade transmission".
But the CDC and the Food and Drug Administration informed state officials late Wednesday that the agencies have resolved the problem with the test kits.
The move was welcomed by public health officials, who have been frustrated by the testing snag.
A whistleblower complaint cited by United States media including The Washington Post and The New York Times said federal health employees were sent to interact with repatriated Americans at the two bases without protective gear or training.
Officials are not too anxious, for now, about casual contact, because federal officials think the coronavirus is spread only through "close contact, being within six feet of somebody for what they're calling a prolonged period of time", said Dr. James Watt, interim state epidemiologist at the California Department of Public Health.
A total of 33 people have been diagnosed with coronavirus in California, and five have since left the state, Newsom said.
He added: "We're still committed to get aggressive containment, and I want the American public to know at this point that the risk is low".
COVID-19 causes symptoms similar to pneumonia, ranging from the mild, such as a slight cough, to the more severe, including fever and difficulty breathing, according to the CDC.
The woman first sought treatment at NorthBay VacaValley Hospital in Vacaville, before her condition worsened and she was transferred to the medical centre.
However, the newest patient, who is a resident of California's Solano County, had no known exposure to the virus through travel or close contact with a known infected individual, according to the California Department of Public Health.
US President Donald Trump has downplayed the potential spread of the novel coronavirus in the country, a message seemingly at odds with senior public health officials who have urged Americans to prepare to cancel mass gatherings and work from home.
With the patient as ground zero, they are interviewing immediate family members.
And in Africa, South Africa's president ordered the evacuation of citizens from the Chinese city of Wuhan, where the virus outbreak began.
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education.