Errors by the US Centers for Disease Control and Prevention and a hospital in San Diego led to a woman with the novel coronavirus being sent back to Marine Corps Air Station Miramar instead of being sent to isolation at the hospital, according to a health official familiar with the situation.

The woman was among Americans in federal quarantine at the base. She flew to the base on February 5 on a State Department flight evacuating Americans from Wuhan, China. The next day she started experiencing symptoms of the novel coronavirus and was taken to UC San Diego Health. Three other people who were exhibiting symptoms were also transported to the hospital.

The hospital sent their specimens to a CDC lab in Atlanta for testing. According to the source, the specimens were incorrectly labeled upon arrival and so they were not tested. The CDC lab did not realize the specimens were from the four Miramar patients.

When no results were reported back, CDC staffers mistakenly gave UC San Diego Health the results of four other patients who tested negative. That mistake led to all four Miramar patients being transferred back to the base Sunday afternoon.

After they arrived back at the base, the mistake was discovered and the tests were run on the four Miramar patients. The results for the woman came back positive, and she was transported back to UC San Diego Health on Monday morning, where she remains in isolation. The woman has had a very mild illness, according to the source, with no fever and a slight cough. The other three patients tested negative.

A spokesperson for the hospital could not be immediately reached for comment.

During a news conference on Tuesday, Dr. Anne Schuchat, principal deputy director of the CDC, said "there was a little bit of a mix-up there” around the testing for the Miramar patient. She added that the patient may have had limited contact with other people when she developed symptoms, but the investigation is ongoing.