United States President Donald Trump has not been tested for the coronavirus, the White House said, despite a number of Republicans announcing they were going into self-quarantine.

Key points: Mr Trump does not have any coronavirus symptoms, the White House says

Mr Trump does not have any coronavirus symptoms, the White House says He announced a possible economic relief to remedy the impact of the virus

He announced a possible economic relief to remedy the impact of the virus Mr Trump's incoming chief of staff, Mark Meadows, will also self-quarantine

United States senator Ted Cruz and House Representatives Paul Gosar, Doug Collins and Matt Gaetz have announced they will self-quarantine after attending a conservative political conference where an attendee later tested positive.

Mr Trump and Vice-President Mike Pence also attended the conference.

Mr Gaetz travelled with Mr Trump aboard Air Force One and Mr Trump also reportedly shook hands with Mr Collins.

"Thank you for everyone's well-wishes and concerns … I should have the COVID-19 test results back tomorrow. Health officials maintain the risk to people I have been in contact with remains low," Mr Gaetz tweeted.

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Mr Cruz also released a public statement through Twitter explaining his encounter with the individual who tested positive, saying the interaction was "a brief conversation and a handshake".

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He said he decided to remain home in Texas this week until a full 14 days have passed since the interaction out of "an abundance of caution".

Republican Representative Mark Meadows, Mr Trump's incoming chief of staff, will also self-quarantine until Wednesday, a spokesperson said.

The White House said there was no indication Mr Trump and Mr Pence came into contact with the infected attendee, and Mr Pence said the risk of the American public contracting the new virus "remains low".

"The President has not received COVID-19 testing because he has neither had prolonged close contact with any known confirmed COVID-19 patients, nor does he have any symptoms," a White House spokesperson said.

"President Trump remains in excellent health, and his physician will continue to closely monitor him."

'Major' steps to prepare economy against coronavirus impact: Trump

Mr Trump and Mr Pence attended the conference where an attendee tested positive for the coronavirus. ( AP: Carolyn Kaster )

The Trump administration scrambled on Monday to assure Americans it was responding to a growing coronavirus outbreak as stock markets plunged and top health officials urged some people to avoid cruise ships, air travel and big public gatherings.



Mr Trump, who has repeatedly played down the threat posed by the flu-like virus sweeping the globe, said he will be taking "major" steps to gird the economy against the impact of the spreading coronavirus outbreak and will discuss a payroll tax cut with congressional Republicans.

"We'll be discussing a possible payroll tax cut or relief, substantial relief, very substantial relief, that's a big number," Mr Trump told reporters.

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Paid sick leave is among policy steps being considered, the official said on condition of anonymity.

White House economic adviser Larry Kudlow advocates specific tax credits, loans or direct subsidies to certain industries or hard-hit areas.

A payroll tax cut could encourage consumer spending and help households that might otherwise struggle to make rent and mortgage payments on time or pay medical bills if family members' work hours are reduced during a coronavirus outbreak.

Democratic candidates Joe Biden and Bernie Sanders said they're consulting with public health experts to plan their next campaign moves.

Senator Sanders cancelled a major rally because of the outbreak and Mr Biden told US media that he would consider doing the same if health authorities said it was necessary.

Mr Biden held a rally in Detroit on Monday and passed out hand sanitiser to attendees and the media.

Florida health officials said everyone returning from China, Iran, South Korea and Italy must isolate for 14 days while travellers from other countries affected by the outbreak should monitor their health.

The number of confirmed US cases reached 605, with 22 deaths, according to the running national tally kept by the Johns Hopkins University.

Thirty-four US states and the District of Columbia have reported to the US Centres for Disease Control and Prevention (CDC) infections of the respiratory illness COVID-19 that can lead to pneumonia.

A nursing home the hardest hit place in US

The dizzying action in financial markets escalated as stocks and oil prices fell. ( AP: Mark Lennihan )

As worries over the virus deepened, the Dow Jones fell a record 2,000 points when trading opened and the S&P 500 posted its largest single-day percentage drop since December 2008, the depths of the financial crisis. A plunge in oil prices contributed to fears of a looming recession.

Mr Trump, who often points to the stock market as a gauge of his economic record, criticised news media organisations' coverage of the outbreak in a tweet and accused Democrats of hyping the situation "far beyond what the facts would warrant".

The CDC advised colleges and universities to consider asking students studying abroad to return home and cancel or postpone upcoming travel.

Several US universities were either moving to virtual instruction or considering the step and limiting gatherings on their campuses.

The hardest-hit place in the United States has been a nursing home in the suburb of Kirkland in the Washington state capital of Seattle, and the state is considering mandatory measures such as banning large gatherings, but not necessarily imposing massive quarantines.

The Life Care Center facility has accounted for most of the 18 confirmed coronavirus-related deaths in Washington state.

The crew of 1,100 from the Grand Princess will be quarantined and treated aboard the ship. ( AP: Noah Berger )

In California, officials planned to offload 2,400 passengers from the Grand Princess cruise ship, which was barred from returning to San Francisco last week due to a coronavirus outbreak on board.

Most of the passengers will go into quarantine at four military bases across the country, with those requiring immediate medical attention heading to hospitals.

The crew of 1,100 will be quarantined and treated aboard the ship unless they need acute care.

California has more than 100 confirmed cases, while on the East Coast, New York state now has 142, Governor Andrew Cuomo said.

New York City Mayor Bill de Blasio asked employers in the nation's most populous city to consider staggering workers' start times to ease crowding on public transport and to allow more telecommuting where possible.

Reuters/AP