Health officials said on Thursday, they are working to identify a number of health care workers who came into contact with the patient who is the first U.S. confirmed case of coronavirus (COVID-19) of unknown origin.

The patient is being treated at UC Davis Medical Center in Sacramento County, the Centers for Disease Control and Prevention said. The health care workers who were exposed are from both UC Davis Medical Center and NorthBay VacaValley Hospital.

Officials said the patient is a woman. CDC is not releasing the patient's identity for privacy reasons.

“There were multiple health care personnel who were exposed to the individual," said Dr. Bela Matyas, public health officer from Solano County at a news conference on Thursday. “At both hospitals we are at present aggressively evaluating everyone who may have had contact with this patient. They are being identified and their risk for exposure is being assessed.”


Some of the health care workers are under isolation and some will be under quarantine. An official with NorthBay Health Care said the number of health care workers exposed is a "moving target" but is less than 100. Dozens of workers who have already been identified have been sent home to monitor their current health status.

Officials from both Solano County Health and Social Services and the CDC spoke at the news conference where they said there is a transition with the mission now focusing on mitigation rather than containment.

The patient being treated at UC Davis Medical Center is the first possible COVID-19 case of community transmission in the U.S. The California Department of Public Health confirmed that the patient is a resident of Solano County. Officials said she was not initially in isolation at either hospital.

Authorities said the person had not recently traveled to a foreign county or had any close contact with someone who had the virus.

Travis Air Force Base in Solano County accepted travelers from China and the Japanese cruise ship for quarantine, but this is the first case of person-to-person transmission.

Dr. Matyas said it was fortuitous that Solano County was already dealing with the repatriation process at the air force base. "The county is prepared to manage this situation," Matyas said.

2 college students in Sacramento came in contact with coronavirus patient

California monitoring 8,400 people for coronavirus

Gov. Newsom: 28 positive coronavirus cases in California

According to a statement from Aimee Brewer, president of North Bay Healthcare Group, the patient had previously received care at NorthBay VacaValley Hospital before being transferred to UC Davis Medical Center.

Brewer said that "at no time did the patient fit the existing CDC criteria for COVID-19, and therefore a test was not immediately administered."

The patient stayed at the hospital facility for three-days and as her condition worsened, she was then transferred to the UC Davis Medical Center for a higher level of care.

Brewer said after learning that a former patient was diagnosed with the coronavirus, the hospital staff was informed. The employees who had contact with the patient were asked to stay home and monitor themselves for any signs of the virus.

An internal email from UC Davis circulating on social media on Wednesday said the patient was transferred from NorthBay VacaValley Hospital on Wednesday, Feb. 19.

"Upon admission, our team asked public health officials if this case could be COVID-19," the letter says. UC Davis requested COVID-19 testing from CDC since neither Sacramento County nor CDPH are providing coronavirus testing at this time. The letter continues to explain that the patient did not meet existing CDC criteria for the test, which was not immediately administered.

According to the memo, the patient was tested on Sunday and the CDC confirmed that the test was positive on Wednesday.

The UC Davis email, first reported by Davis Enterprise, is signed by health officials at UC Davis including the vice-chancellor of Human Health Sciences.

UC Davis letter circulating on social media

On Thursday UC Davis officials said as an abundance of caution, three people living on campus at Kearney Hall are currently in isolation.

"CDC is testing one of them for COVID-19, and this person is not on campus. The other two individuals are asymptomatic, meaning they are not showing any symptoms of illness, so, following CDC guidance, they have not been tested."

To date there are no confirmed cases of the virus in Yolo County or on the UC Davis main campus.

The school is stepping up preventative efforts by adding daily disinfection practices within all student housing and dining service properties.

According to the CDPH, while the health risk from the virus to the general public remains low, the state is working to prevent the spread of the coronavirus.

Scientists have already begun the process of contact tracing to determine how the patient might have become infected.

Experts on a panel at UC Berkeley say that right now, not much is known about how long the virus can exist outside the human body. There are cases of transmission through airborne particles. Screening people who don't show symptoms is difficult.

Don't forget to download the new and improved KTVU mobile app

"The problem at this moment is people are not sick, but are carriers, so there's almost no way to see which one is really infected," Fenyang Liu, UC Berkeley professor of public health said. "[It may be] almost impossible to stop transmission but we can do much better in quarantining or containing the virus."

People in Vallejo were concerned.

"I would like to know if there's anyone diagnosed with the disease living in my town. That is very concerning. Very serious. And I know it's been predicted that it's going to spread worldwide," said Martha Morales in Vallejo.

Darnell Jones also said he found "it alarming. I mean, it just confirms that it's here and it's something we have to prepare for and get ready for. It's here. We can't run from it. Only thing we can do is prepare."

On Thursday, Solano County declared a local emergency over the virus to bolster its response efforts in preventing it from spreading.

2019 Novel Coronavirus (first detected in Wuhan, China) illustration provided by US Centers for Disease Control and Prevention, on texture, partial graphic. (AP Images)

This story was reported from Oakland, Calif.