California health officials have confirmed a second person in the US who did not travel internationally has tested positive for the strain of coronavirus known as Covid-19.
Health officials in San Jose said the patient was an older adult woman with chronic health conditions who does not have a travel history or any known contact with a traveller or infected person.
It comes a day after state officials said a woman hospitalised in Sacramento had contracted the illness after no known contact.
Dr Cody said the newly confirmed case in Santa Clara County is not linked to two previous cases in that county, nor to others in the state.
The Santa Clara County resident was treated at a local hospital
At least 124 registered nurses and other health care workers from the hospital were sent home for self-quarantine after the woman with the virus was admitted, National Nurses United, a nationwide union representing registered nurses said.
The case of the infected women marks an escalation of the worldwide outbreak in the US because it means the virus could spread beyond the reach of preventative measures like quarantines.
However state health officials said that was inevitable and that the risk of widespread transmission remains low.
Besides the woman, all the other cases in the US have been for people who travelled abroad or had close contact with others who travelled.
Earlier US cases included 14 in people who returned from outbreak areas in China, or their spouses; three people who were evacuated from the central China city of Wuhan and 42 American passengers on the Diamond Princess cruise ship.
The number of global people sickened by the virus hovered around 83,000 on Friday and there were more than 2,800 deaths, most of them in China.