US reports third case of novel coronavirus of unknown origin

US health officials on Friday reported a third case of the new coronavirus transmitted to a person who did not travel overseas or come in contact with anyone known to be ill, indicating the disease was spreading in the country.

Authorities said the new case concerned a person living in the western state of Oregon. The adult patient, who has been hospitalised, was known to have had contact with people at an elementary school.

Oregon Health Authority director Patrick Allen told reporters that the case is considered "presumptive" pending confirmation of the test results from the Centers for Disease Control and Prevention.

"We've been expecting this and we're prepared for it," he said.

Officials said the elementary school will be shut down until March 4 as it undergoes a deep clean and as health officials talk to employees and parents.

Two other "community spread" cases have been reported in neighboring California this week.

Both cases involve older people in the northern part of the state who mysteriously contracted the virus.

The increasing number of people stricken with the illness in the United States is sure to heighten fears of an outbreak across the country.

According to the Centers for Disease Control, as of Thursday there were more than 60 people infected with the disease in the United States.

California's Governor Gavin Newsom on Thursday said 33 people there had tested positive for the virus, and five of them had left the state.

Worldwide more than 84,000 people have been infected with the disease and 2,870 have died.