Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

The head of a health system in Sacramento, California, says the Centers for Disease Control and Prevention did not immediately test a patient infected with the new coronavirus, in what may be the first case of community spread in the U.S.

Dr. David Lubarsky, CEO of University of California, Davis, Health, said in a note to staff obtained by NBC News that after the patient was transferred to UC Davis Medical Center on Feb. 19, it asked the CDC to conduct testing, but the federal agency declined.

"We requested COVID-19 testing by the CDC, since neither Sacramento County nor CDPH is doing testing for coronavirus at this time," said the note, which was signed by Lubarsky and UC Davis Medical Center interim CEO Brad Simmons. (CDPH stands for California Department of Public Health.)

"Since the patient did not fit the existing CDC criteria for COVID-19, a test was not immediately administered. UC Davis Health does not control the testing process," the two officials wrote in the letter.

On Sunday, the CDC reversed its decision and ordered the test, and on Wednesday, the agency confirmed that the patient had tested positive, Lubarsky and Simmons wrote.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

The CDC did not immediately respond to a request for comment late Wednesday.

Lubarsky and Simmons wrote that from the time the patient was transferred to UC Davis Medical Center, precautions were taken to prevent exposure because it suspected a viral infection.

"This is not the first COVID-19 patient we have treated, and because of the precautions we have had in place since this patient's arrival, we believe there has been minimal potential for exposure here at UC Davis Medical Center," the memo said. It was later posted to the UC Davis Health website.

Full coverage of the coronavirus outbreak

The case is still being investigated, but it could be the first case of person-to-person transmission of the illness caused by the new coronavirus in the general public in the United States.

The patient had no known exposure to the virus through travel or close contact with a known infected person, the state health department said.

There have been at least two other person-to-person transmission cases in the U.S., but both involved spouses of people who had traveled to China. A man in Chicago whose wife traveled to the Chinese city of Wuhan tested positive, and the couple were released from a hospital earlier this month.

The other case involved a husband and wife in San Benito County in Northern California. The husband had recently traveled to the Wuhan, but his wife had not, authorities have said.

The coronavirus outbreak has spread from China to at least 40 countries, affecting markets and disrupting travel. A recent increase in cases in Italy, Iran and South Korea has heightened concerns about the ability to contain the spread of the virus.

Cases in the U.S. have been limited, although the CDC said Americans should prepare for the spread of the coronavirus in communities.