Chinese health authorities did not immediately conform the report from state broadcaster CCTV.

Coronaviruses are spread through coughing or sneezing or by touching an infected person. Some cause the common cold and others can lead to more severe respiratory diseases, such as SARS and MERS.

The novel coronavirus is different from those that have previously been identified, CCTV said.

As of Sunday, the Wuhan Municipal Health Commission said 59 people in the central Chinese city were being treated for the respiratory illness. Seven were in critical condition, while the rest were stable.

Laboratory experts as of Wednesday evening had found the novel coronavirus in 15 of those cases, CCTV said, adding that more research must be done before a conclusion is reached.

Possible cases of the same illness have been reported in Hong Kong and South Korea involving recent travelers to China.

SARS, or severe acute respiratory syndrome, first infected people in southern China in late 2002, and the illness spread to more than two dozen countries. More than 8,000 people were sickened and nearly 800 died, but none have been reported since 2004.  The new illnesses had raised fears of a SARS recurrence.

Another coronavirus caused MERS, or Middle East respiratory syndrome. That outbreak started in Jordan and Saudi Arabia in 2012 and spread into about two dozen other countries. About 2,500 lab-confirmed cases have been reported, including more than 800 deaths, with cases continuing to be seen in recent years.

On Wednesday, the U.S. Centers for Disease Control and Prevention put out a health alert advising physicians who treat patients with pneumonia-like illness to consider a possible link to the Chinese outbreak and to wear masks and take other precautions in treating patients who recently traveled to Wuhan.

The CDC this week also advised U.S. travelers going to Wuhan to avoid animals and sick people and wash their hands often.