A second person has died from the coronavirus in King County, near Seattle, Washington, authorities have confirmed.

The victim was a man in his 70s with an underlying health condition who was being treated at Evergreen Health hospital in Kirkland, the same facility at which a man in his 50s died late on Friday.

Meanwhile, authorities have said three more people in Washington have tested positive for Covid-19, a man in his 70s, a woman in her 80s and another woman in her 90s.

Health officials have been testing 50 people who have been suffering from respiratory illnesses at an elderly care home in the area. Two of the first people people confirmed to have the coronavirus are connected to the home, one a resident and one an employee.

Earlier it was announced that the first case of the deadly virus had been confirmed in New York. A woman in her late thirties who recently travelled to Iran was being quarantined in her home, according to the New York Times.

The response to Coronavirus in Daegu South Korea Show all 11 1 /11 The response to Coronavirus in Daegu South Korea The response to Coronavirus in Daegu South Korea Visitors with suspected symptoms of the new coronavirus, inside of a car, bottom right, get virus test by members of medical team as others queue in their cars at a "drive-through" test facility at Yeungnam University Medical Center in Daegu on 27 February 2020 AP The response to Coronavirus in Daegu South Korea Workers move equipment into containers set up as a makeshift medical facility to accommodate COVID-19 patients at a hospital's grounds in Daegu, South Korea on Friday 28 February 2020 AP The response to Coronavirus in Daegu South Korea People wait in line to buy face masks in front of a store at Dongseongro shopping district in Daegu on 27 February 2020 AFP via Getty Images The response to Coronavirus in Daegu South Korea Medical workers wearing protective gears comfort each other outside a hospital in Daegu, South Korea, on 28 February 2020 REUTERS The response to Coronavirus in Daegu South Korea Medical staff in protective gears arrive for a duty shift at Dongsan Hospital in Daegu South Korea on Friday 28 February 2020 AP The response to Coronavirus in Daegu South Korea A South Korean health worker sprays disinfectant as part of preventive measures against the spread of the COVID-19 coronavirus, at a residential area near the Daegu branch of the Shincheonji Church of Jesus in Daegu on 27 February 2020 AFP via Getty Images The response to Coronavirus in Daegu South Korea A man wears a mask and goggles as he waits in line to buy face masks from a post office near the Daegu branch of the Shincheonji Church of Jesus in Daegu on 27 February 2020 AFP via Getty The response to Coronavirus in Daegu South Korea South Korean medical workers wearing protective gear visit a residence of people with suspected symptoms of the COVID-19 coronavirus to take samples, near the Daegu branch of the Shincheonji Church of Jesus in Daegu on 27 February 2020 AFP via Getty Images The response to Coronavirus in Daegu South Korea A South Korean health worker sprays disinfectant as part of preventive measures against the spread of the COVID-19 coronavirus, at a residential area near the Daegu branch of the Shincheonji Church of Jesus in Daegu on 27 February 2020 AFP via Getty Images The response to Coronavirus in Daegu South Korea A South Korean army vehicle sprays disinfectant on a road to prevent the spread of the COVID-19 in Daegu, South Korea on Thursday 27 February 2020. AP The response to Coronavirus in Daegu South Korea Troops set up makeshift partitions and beds at the Armed Forces Hospital in Daegu South Korea 28 February 2020 EPA

A statement from Governor Andrew Cuomo's office confirmed the case on Sunday night but did not reveal the exact location of the woman.

Vice president Mike Pence, who has been put in charge of the government's response to the coronavirus crisis, had said it was possible that more Americans would lose their lives to the virus, but stressed that most people were not in danger.

The coronavirus may have been circulating for weeks undetected in Washington, a preliminary finding that could mean hundreds of undiagnosed cases, researchers have revealed after analysing the genetic sequences of viruses from two people.

Researchers at the Fred Hutchinson Cancer Research Center and the University of Washington said they had evidence the virus may have been circulating in the state for up to six weeks undetected.

Trevor Bedford, an associate professor who announced the preliminary findings on the virus in Washington state, said on Twitter late on Saturday that genetic similarities between the state's first case on 20 January and a case announced on Friday indicated the newer case may have descended from the earlier one. The first of those two was the first case discovered in the United States.

"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," he said on Twitter.

In California, two health care workers in the San Francisco Bay area who cared for an earlier coronavirus patient were diagnosed with the virus on Sunday, the Alameda and Solano counties said in a joint statement.

The health care workers are both employed at NorthBay VacaValley Hospital in Vacaville, California, and had exposure to a patient treated there before being transferred to UC Davis Medical Center in Sacramento, the statement said. That patient was the first person in the US discovered to have contracted the coronavirus with no known overseas travel.

Alameda County declared a state of emergency on Sunday following the news.

Elsewhere, authorities announced new cases in Illinois and Rhode Island.