WASHINGTON (REUTERS) - New York state confirmed its first positive coronavirus case, Governor Andrew Cuomo said on Sunday (March 1) as the United States government said it would start screening travellers for the virus and hike production of protective masks.

Mr Cuomo said on Twitter that a woman in her 30s contracted the coronavirus during a recent trip to Iran and was in quarantine in her home. He did not say where the woman lived.

"The patient has respiratory symptoms, but is not in serious condition and has been in a controlled situation since arriving in New York," he said.

At the federal level, President Donald Trump's administration scrambled on Sunday to reassure Americans as the disease spreads and businesses cancel conferences and flights.

Administration officials tried to calm market fears that the coronavirus could cause a global recession, saying the public had overreacted and that stocks would bounce back because of the underlying strength of the US economy.

The first American died from coronavirus, a man in his 50s with underlying conditions in Washington state, officials said last Saturday. They still do not know how he contracted the disease.

The state on Sunday confirmed two other cases and locked down a long-term care facility where a resident and a worker also tested positive for coronavirus and 50 residents and staff are showing symptoms.

Over 70 cases have been reported in the US, with most on the West Coast, but new cases have also emerged in the Chicago area and Rhode Island, aside from New York.

Stock markets plunged last week, with an index of global stocks setting its largest weekly fall since the 2008 financial crisis, and more than US$5 trillion (S$7 trillion) wiped off the value of stocks worldwide.

A key energy conference in Houston that brings together oil ministers and energy firms was cancelled on Sunday, with the organisers of CERAWeek noting that border health checks were becoming more restrictive and companies had begun barring non-essential travel to protect workers.

A world economy conference with Pope Francis due to take place in Italy later this month was also cancelled.

Mr Trump said on Sunday that travellers to the US from countries at high risk of coronavirus would be screened before boarding and on arrival, without specifying which countries.

Delta Air Lines said on Sunday it was suspending until May flights to Milan in northern Italy where most of that country's coronavirus cases have been reported. Flights will continue to Rome. American Airlines Group announced a similar move late last Saturday.

The US has 75,000 test kits for coronavirus and will expand that number "radically" in coming weeks, US Health and Human Services Secretary Alex Azar told ABC's This Week on Sunday.

Vice-President Mike Pence said the government had contracted 3M to produce an extra 35 million respiratory masks a month. He urged Americans not to buy the masks, which he said were needed only by healthcare workers. Honeywell International is the other major US mask producer.

He also told Fox News that clinical trials of a coronavirus vaccine would start in six weeks but that a vaccine would likely not be available this season.

Democrats, who will challenge Mr Trump for the presidency in the Nov 3 election, have criticised his administration for downplaying the crisis and not preparing for the disease to spread in the US.

Mr Pence, whom Mr Trump appointed last week to run the White House's coronavirus response, said Americans should brace for more cases but that the "vast majority" of those who contracted the disease would recover.

"Other than in areas where there are individuals that have been infected with the coronavirus, people need to understand that for the average American, the risk does remain low. We're ready," Mr Pence told NBC's Meet the Press.

The US has imposed limits on travellers who have visited Iran and recommended against travel to hard-hit areas of Italy and South Korea.

Mr Trump said last Saturday that the US was also considering shutting the country's southern border with Mexico to control the spread of the virus, adding: "We hope we won't have to do that."

Mexico has reported four coronavirus cases. Its Foreign Ministry said last Saturday that both governments were in "close and effective communication, especially the health authorities".