A second patient with a confirmed case of coronavirus, or COVID-19, is being treated at UC San Diego Medical Center, a Centers for Disease Control and Prevention spokesperson said Wednesday. It's the second confirmed case in the county since the deadly outbreak began.

The first case was confirmed by the CDC on Monday. Both patients were among the 232 Americans evacuated from Wuhan, China, last week and flown to Marine Corps Air Station Miramar to complete a 14-day federal quarantine.

The patients had no physical contact with each other while in quarantine and there is no indication the virus is spreading person-to-person within the quarantine facility, according to Dr. Chris Braden, the on-site CDC lead at MCAS Miramar.

The patients arrived at the base on separate planes -- the first landed Feb. 5 and the second on Feb. 7 -- and were housed in separate facilities, the CDC said.

On Sunday, four patients who had been taken from the base to UC San Diego Medical Center earlier in the week were discharged by the CDC back to the base after their tests came back negative, hospital spokesperson Michelle Brubaker said.

Soon after a woman (Patient 1) was discharged, the CDC notified her that her test results were mislabeled due to pseudonyms used for privacy reasons, and she, in fact, tested positive for the virus, according to a CDC spokesperson.

The woman was told to stay in her room at the base while she was retested and stayed out of contact with others, the official said. She was then taken back to the hospital Monday morning.

NBC 7's Artie Ojeda has more information on the second plane that landed in MCAS Miramar from Wuhan, China.

A plane carrying 167 U.S. citizens landed at the base on Feb. 5, and a second plane carrying 65 more landed two days later.

A 3-year-old girl aboard the first flight was taken away from the base when her evacuation plane landed. After three days in isolation, she returned to the MCAS Miramar. But on Tuesday, she was placed back in isolation at Rady Children's Hospital for additional tests.

By Sunday, seven people -- including Patient 1, the 3-year-old girl, and the toddler's father -- had at one point been removed from quarantine at the base and placed in isolation at area hospitals for further testing. All seven were passengers on the first evacuation flight from China to land in San Diego.

Another person quarantined at the base was isolated at UC San Diego Medical Center Monday, according to Brubaker.

A group of quarantined Americans on Tuesday drafted a petition calling for better oversight at the facility.

NBC 7's Dave Summers breaks down a news conference held Tuesday by the CDC and county health officials.

The unnamed writer said the suggestions are "critical measures toward mitigating the potential risk of spreading the virus at the Miramar Center," on behalf of "Wuhan evacuees at Miramar Marine Air Base."

The outbreak has infected over 60,000 people worldwide and killed more than 1,300.

Check back for updates on this developing story.