A Northern California woman who tested positive for COVID-19 is in serious condition and has been intubated.

Rep. John Garamendi (D-Calif.), who represents the district where the woman is from, told CNN the patient is potentially unable to talk, hampering efforts to determine where she might have encountered the coronavirus that causes COVID-19.

The Centers for Disease Control and Prevention has dispatched 10 officials to track down anyone who may have come in contact with the Solano County woman, whose source of infection remains a mystery. Health officials believe she could be the first case of community spread of the virus in the United States.

Because she hadn’t traveled to any countries currently experiencing an outbreak or been in contact with anyone known to be infected, she was not immediately tested for the virus under CDC guidelines and went undiagnosed for several days.

Those guidelines have since been updated, CDC Director Dr. Robert Redfield said Thursday.

“As soon as that case was recognized, we met and we revised our case definition for persons under investigation,” Redfield said. “Today, that has been posted [to the CDC website] along with a new health advisory that the recommendation should be when a clinician or individual suspects coronavirus, then we should be able to get a test for coronavirus.”

The patient was transferred to UC Davis Medical Center in Sacramento as her condition worsened, where she is currently receiving treatment. She is the 60th confirmed case of the virus in the U.S., according to the hospital.

Solano County Public Health officials are bracing for what could be a cluster of cases in Northern California, where frustration over the CDC’s earlier, more restrictive testing guidelines is apparent.

“So this person in Northern California, who didn’t travel to China, who we don’t know where [she] got the coronavirus, [she] could have passed it on to two more people, who passed it on to two more people, who passed it on to two more people,” Rep. Ted Lieu, (D-Calif.) told the foreign affairs subcommittee that focuses on Asia and the Pacific on Thursday.

“So there could be a whole cluster of cases, but until as of yesterday, we don’t know because we weren’t testing anyone who didn’t travel to China.”

Solano County has declared a local emergency and is urging residents to consult with health care providers if they develop any flu-like symptoms, including fever, cough and shortness of breath. Individuals should call ahead before seeking medical care in person for guidance on how to prevent possibly transmitting the virus to health care workers and other patients.

Meanwhile, the CDC recommends these everyday actions to help prevent the spread of the disease and avoid getting sick:

Avoid close contact with people who are sick.

Avoid touching your eyes, nose and mouth.

Stay home when you are sick.

Cover your cough or sneeze with a tissue, then throw the tissue in the trash.

Clean and disinfect frequently touched objects and surfaces using a regular household cleaning spray or wipe.

The CDC does not recommend that people who are well wear a face mask to protect themselves from respiratory diseases, including COVID-19.

Face masks should be used by people who show symptoms of COVID-19 to help prevent the spread of the disease to others.

The use of face masks is also crucial for health workers and people who are taking care of someone in close settings (at home or in a health care facility).

Wash your hands often with soap and water for at least 20 seconds, especially after going to the bathroom; before eating; and after blowing your nose, coughing, or sneezing.

If soap and water are not readily available, use an alcohol-based hand sanitizer with at least 60% alcohol. Always wash hands with soap and water if hands are visibly dirty.