The patient who tested positive was evacuated from Wuhan, the epicenter of the virus, and isolated at a hospital near Joint Base San Antonio-Lackland.
More than 1,100 people have died, almost all of them in China, where there are more than 44,000 confirmed cases.
Travelers arrive to LAX Tom Bradley International Terminal wearing medical masks for protection against the novel coronavirus outbreak in Los Angeles, Calif., on February 2, 2020.
Of the almost 1,000 people who were evacuated from Wuhan, three have tested positive for the virus, including Thursday's case. The delay in diagnosis might contribute to the disease's spread as patients under investigation (PUI) will remain unconfirmed as having the disease. She was returned to the hospital on Monday after testing positive for the virus.
Tens of thousands of cases of the illness, known as COVID-19, have been reported globally, the vast majority of them in China. It's responsible for the planning, coordination and conduct of immunization programs in the United States.