Fears of an outbreak in Washington deepen after a second patient in the state died from coronavirus.
The patient was a man in his 70s who was treated in the same facility where the first patient died a day earlier.
Twenty-three new cases of Covid-19, the illness caused by the virus, were reported in the US over the weekend, bringing the total to 88 cases.
The first two Covid-19 deaths on US soil prompted Washington State to declare a state of emergency.
New cases were reported in US states from coast to coast, in Washington, California, Oregon, Illinois, Florida, New York and Rhode Island.
New York Governor Andrew Cuomo disclosed on Monday that the patient in his state is a 39-year-old female health care worker who had been in Iran before returning to the US last week.
The woman did not take public transportation and is not believed to have been contagious either on the plane or in the car returning home. Her spouse, also a healthcare worker, is being tested.
There is “no doubt” more cases will be identified, Mr Cuomo said, but urged against panic.
Also on Monday, officials in Florida said the two presumed cases in the state have been found in a man in his 60s and a woman in her 20s who had returned from Northern Italy.
The first of the US cases were announced on 21 January, with 65 cases in the country as of last Friday.
The weekend brought a sharp rise in numbers, raising concerns. Of the existing cases, some patients are believed to have travelled to high-risk countries, while others are thought to have contracted the virus from within the US.
Officials on the US West Coast – in Washington, California and Oregon – have expressed concerns about cases appearing in patients who had not visited an area where there was an outbreak or been in contact with anyone who had.
Researchers who studied the two Washington deaths have said that the virus may have been spreading for weeks, and suggested that up to 1,500 people may have been infected.
The second US patient to die of the coronavirus infection was being treated at the EvergreenHealth hospital in Kirkland, Washington – the same facility to identify the country’s first death on Saturday, a man in his 50s. Both patients had underlying health conditions, officials said.
The federal government has admitted to problems with its diagnostic testing amid the rise in cases. A top federal scientist has raised concerns about a possible contamination in an Atlanta lab where the government had made test kits for the virus, Axios reports.
More than 85,000 Covid-19 cases have been reported in 57 countries around the world, causing over 3,000 deaths, according to the World Health Organization. The majority of infections and deaths are in China, where the virus emerged late last year.
On Sunday, another 573 new cases of Covid-19 were confirmed in China, in the highest daily increase in a week. The latest figures bring the total number of infections to 79,824 in China.
Thirty-five deaths were also announced in China, all but one in the worst-affected Hubei province.