SAN FRANCISCO (CBS SF) — Calling it an “early warning system,” Health and Human Services Secretary Alex Azar announced Friday that flu patients in San Francisco, Seattle, New York, Los Angeles and Chicago would also undergo testing for the coronavirus.

In an interview on CNBC, Azar said the threat of the illness was quite low, but that status always has the potential to change rapidly.

“We’re deploying the full force of the U.S. government to protect the health and safety of the American people,” he said.

In China, the illness had sickened 63,851 people by the end of Thursday, up 5,090 from the previous day. The death toll, meanwhile, has risen to 1,380.

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California has had the most confirmed cases of coronavirus in the United States with nine, of those four have been in the Bay Area. There have been two confirmed cases in Santa Clara County and a husband and wife from San Benito County were being treated at UC-San Francisco Hospital.

The symptoms of the flu can be very similar to the coronavirus so Azar said his agency deployed an “an early warning system” on Thursday, ordering the testing of flu patients for the coronavirus in five cities.

“We are using our flu surveillance network in Seattle, San Francisco, L.A., Chicago and New York, where individuals who present with flu-like or China coronavirus-like symptoms will be tested not just for flu but also tested for China coronavirus,” he told CNBC. “That way we have an early warning system. We have no epidemiological reason to believe that we have cases out there, but we want to be on the safe side.”

Later in the day, the Centers for Disease Control and Prevention said the testing would not be taking place in hospitals but in samples sent to five public health labs in San Francisco, Los Angeles, Seattle and Chicago.

CDC spokesman Richard Quartarone said his agency will release more details on how the testing program will roll out next week.

Azar also said his agency was closely monitoring the growing coronavirus outbreak in Singapore, where 67 cases have been confirmed.

“We are accessing the information hour-by-hour,” he said when asked about the Singapore outbreak and possible travel restrictions. “We will take the steps that are warranted if the data supports that. With Singapore, one of the questions is whether we are seeing true multi-generational community spreading…or if we are actually seeing a first generation cluster that is really not that kind of multi-generational spread. We got to get to the bottom of it.”

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In another development Friday, several news agencies reported that a man on United Airlines Flight 901 from San Francisco to London was taken off the plane Friday on a stretcher after displaying possible signs of the coronavirus.

According to passenger reports on social media, the ill traveler was isolated at the back of the plane and then transported to a hospital. The other passengers were required to fill out a Health England contact form and then allowed to disembark.

Zeng Yixin, vice director of the National Health Commission in China, announced Friday that more than 1,700 Chinese medical workers have been infected by the new virus.

Six of the workers have died, Zeng said at a news conference.

The health commission is “highly concerned about this issue” and has issued guidelines for the prevention and control of infection within medical institutions, he said.

Medical workers account for about 3.8% of confirmed cases as of three days ago, Zeng said.

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Elsewhere, Japan confirmed seven more cases, a day after it reported its first death from the virus. Japan now has 258 confirmed cases, including 218 from a cruise ship, the Diamond Princess, that has been quarantined in Yokohama.

Health officials allowed 11 elderly passengers to leave the ship on Friday after they tested negative for the virus. They are the first group of dozens of older passengers expected to get off the vessel before their 14-day quarantine period ends on Feb. 19 to reduce risks of their health deteriorating.

Japanese Health Minister Katsunobu Kato on Thursday said passengers age 80 or older with chronic health issues or in cabins without windows that can open will be able to leave the ship if they pass the virus test.

More than 580 cases have been confirmed outside mainland China and three deaths, one each in the Philippines and Hong Kong and now a Japanese woman in her 80s. Health officials are investigating how she got infected.

© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.