Earlier Sunday, California officials confirmed the third and fourth cases in that state, one in Orange County and one in Los Angeles County. The first two U.S. cases, confirmed last week, involved one patient in the Seattle area and one in Chicago.

A fifth U.S. case of coronavirus has been confirmed in Arizona's Maricopa County. A statement released on Sunday from the Arizona Department of Health Services described the patient as "a member of the Arizona State University community who does not live in university housing." The news was also confirmed by Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention, in a press call with reporters. Earlier Sunday, California officials confirmed the third and fourth cases in that state, one in Orange County and one in Los Angeles County. The first two U.S. cases, confirmed last week, involved one patient in Chicago and one in the Seattle region. All five U.S. patients had traveled previously to Wuhan, China, the epicenter of the infectious disease outbreak, and all five remain hospitalized for now, Messonnier said. The CDC has just over 100 persons "under investigation" for the new strain of coronavirus in 26 states, said Messonnier. So far, 25 of those have tested negative for the virus, and 5 positive.

The CDC will begin updating these numbers on its website three times a week — Mondays, Wednesdays and Fridays — starting tomorrow on Monday, Jan. 27. "We expect to find more cases of novel coronavirus in the United States," Messonnier said. Local health workers across the U.S. have been reaching out to the CDC for guidance on how to screen, manage and treat potential cases of the disease. Currently, testing for the virus must take place at CDC. "We are getting calls all day, all night from clinicians. That's what we want." She called the inquiries "a good sign" — evidence that the country's public health system is working. She described the overall health risk in the U.S. from the virus as "low," adding that "at this time in the United States, '2019 novel coronavirus' is not spreading in our communities."