A second coronavirus case of unknown origin has been confirmed in the United States, health officials in the San Francisco Bay Area announced Friday.

The case in Santa Clara County comes after authorities two days earlier said a woman in Solano County may have been the first case in the country to contract the virus through exposure in the community. Both incidents have placed Northern California as the epicenter of what officials are calling the turning point in the spread of the highly contagious coronavirus.

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“This new case indicates that there is evidence of community transmission but the extent is still not clear,” said Dr. Sara Cody, Health Officer for Santa Clara County and Director of the County of Santa Clara Public Health Department. “I understand this may be concerning to hear, but this is what we have been preparing for. Now we need to start taking additional actions to slow down the spread of the disease.”

The new case is the third confirmed case of coronavirus in Santa Clara County. The woman in this latest confirmed case did not travel to any coronavirus-affected areas or knowingly come into contact with an infected person, officials said.

Authorities said the new confirmed case in Santa Clara County also is not tied to the Diamond Princess cruise ship, which was docked in Japan with passengers quarantined. Passengers were evacuated, with dozens transported earlier this month to Travis Air Force Base in Fairfield for coronavirus quarantine.

Santa Clara County health officials address a second coronavirus case of unknown origin confirmed in the United States.

Several of those passengers have since been transported to other Bay Area hospitals for treatment and isolation.

Meanwhile, officials continue to investigate the incident involving a Solano County woman who may be the first United States case of coronavirus with no known origin. Infectious disease experts fanned out in Vacaville, where the woman sought treatment at a hospital before she was tested and confirmed to have coronavirus.

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Public health officials have identified 93 people who have had contact with the woman. They have been asked to self-quarantine, with a few who have shown symptoms in isolation.

The infected woman is currently being treated at UC Davis Medical Center.

Besides the woman, at least 60 other cases in the U.S. have been for people who traveled abroad or had close contact with others who traveled.

Earlier U.S. 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 global count of those sickened by the virus hovered Friday around 83,000 and caused more than 2,800 deaths, most of them in China.

The Associated Press contributed to this report.