Health officials in Washington state said on Sunday a second person infected with the coronavirus had died there, while New York's governor said his state confirmed its first case of the illness.
The Washington death was in the Seattle area and was reported on the website of the Seattle and King County public health department. On Saturday, the same officials reported the first death from coronavirus in the United States.
New York state confirmed its first positive coronavirus test, Governor Andrew Cuomo said on Sunday night. He wrote on Twitter that a woman in her 30s contracted coronavirus during a recent trip to Iran and was in quarantine in her home. He did not say where the woman lived, but the New York Times, citing unnamed state officials, said the woman was in New York City.
"The patient has respiratory symptoms, but is not in serious condition and has been in a controlled situation since arriving in New York," Cuomo 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 U.S. economy.
Washington state on Sunday confirmed two other cases at a long-term care facility where a resident and a worker also tested positive for coronavirus and 50 residents and staff were showing symptoms.
Over 70 cases have been reported in the United States, with most on the West Coast but new cases 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 $5 trillion wiped off the value of stocks worldwide.
A key energy conference in Houston that brings together oil ministers and energy firms was canceled on Sunday with the organizers 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 canceled.
Trump said on Sunday that travelers to the United States from countries at high risk of coronavirus would be screened before boarding and on arrival, without specifying which countries.
Delta Air Lines Inc 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 Inc announced a similar move late on Saturday.
The United States has 75,000 test kits for coronavirus and will expand that number "radically" in coming weeks, U.S. Health and Human Services Secretary Alex Azar told ABC's "This Week" on Sunday.
Vice President Mike Pence said the government had contracted 3M Co to produce an extra 35 million respiratory masks a month. He urged Americans not to buy the masks, which he said were only needed by healthcare workers. Honeywell International Inc is the other major U.S. 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 Trump for the presidency in the Nov. 3 election, have criticized his administration for downplaying the crisis and not preparing for the disease to spread in the United States.
Pence, whom 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," Pence told NBC's "Meet the Press."
The United States has imposed limits on travelers who have visited Iran and recommended against travel to hard-hit areas of Italy and South Korea.
Trump said on Saturday that the United States 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 on Saturday that both governments were in "close and effective communication, especially the health authorities."