A second man has died from coronavirus in the United States, officials have confirmed.
The victim – a man in his 70s – died in Washington state on Saturday, the same state where the country’s first victim also died.
Researchers fear the covid-19 virus may have been circulating in the Seattle area for weeks, with two more men in their 60s also in critical condition.
Authorities said both victims had underlying health conditions and were treated at a hospital in Kirkland, Washington.
Two healthcare workers in California have also been diagnosed with the disease, while elsewhere, authorities announced a third case in Illinois and the first cases in New York state.
Worried Americans have swarmed shops to stock up on basic goods such as bottled water, canned foods and toilet paper.
US Vice President Mike Pence and Health and Human Services Secretary Alex Azar sought to reassure the American public that the federal government is working to make sure state and local authorities are able to test for the virus.
Both said during a round of TV talk show appearances on Sunday that thousands more testing kits had been distributed to state and local officials, with thousands more to come.
“They should know we have the best public health system in the world looking out for them,” Mr Azar said, adding that additional cases will be reported and the overall risk to Americans is low.
As Americans prepared, researchers at the Fred Hutchinson Cancer Research Centre and the University of Washington said they had evidence the virus may have been circulating in the state for up to six weeks undetected.
This could mean there are hundreds of undiagnosed cases in the area.
They posted their research online but it was not published in a scientific journal or reviewed by other scientists.
Trevor Bedford, an associate professor who announced the preliminary findings on the virus in Washington state, said on Twitter on Saturday that genetic similarities between the state’s first case on January 20 and a case announced on Friday indicated the newer case may have descended from the earlier one.
The January 20 case was the first known case in the US and Mr Bedford said: “I believe we’re facing an already substantial outbreak in Washington State that was not detected until now due to narrow case definition requiring direct travel to China.”
There are now more than 80,000 cases of Covid-19 worldwide and about 3,000 deaths.
UK Prime Minister Boris Johnson will chair a meeting of the Cobra committee later on Monday to discuss the outbreak in Britain.
Agencies contributed to this article