As groceries and other stores reported exceptional demand over the weekend as people raced to stock up on essentials, officials declared the Pacific Northwest was now at the centre of the country’s biggest health crisis for a generation.

The latest deaths follow recent reports of two other people in the area who have died as doctors in the state believe the virus travelled undetected for several weeks.

Reports of infections of the flu-like respiratory illness have climbed to nearly 80 in the US.

The Centres for Disease Control and Prevention has confirmed 16 cases, though it presumes another 27 cases will test positive for the virus. Officials anticipate more confirmed cases in the coming days and weeks.

Streets of Venice empty due to Coronavirus fears Show all 16 1 /16 Streets of Venice empty due to Coronavirus fears Streets of Venice empty due to Coronavirus fears Gondoliers wait for customers in Venice, Italy, Friday, Feb. 28, 2020. Authorities in Italy decided to re-open schools and museums in some of the areas less hard-hit by the coronavirus outbreak in the country which has the most cases outside of Asia, as Italians on Friday yearned for a return to normal life even amid fears that the outbreak could plunge the country's economy into recession. AP Streets of Venice empty due to Coronavirus fears Gondoliers wait for customers in Venice, Italy, Friday, Feb. 28, 2020. Authorities in Italy decided to re-open schools and museums in some of the areas less hard-hit by the coronavirus outbreak in the country which has the most cases outside of Asia, as Italians on Friday yearned for a return to normal life even amid fears that the outbreak could plunge the country's economy into recession. AP Streets of Venice empty due to Coronavirus fears A man wearing a protective mask walks past the Ponte di Rialto (Rialto Bridge) in Venice, Italy, Friday, Feb. 28, 2020. Authorities in Italy decided to re-open schools and museums in some of the areas less hard-hit by the coronavirus outbreak in the country which has the most cases outside of Asia, as Italians on Friday yearned for a return to normal life even amid fears that the outbreak could plunge the country's economy into recession. AP Streets of Venice empty due to Coronavirus fears A gondolier on the Grand Canal as the sun sets in Venice, Italy, Friday, Feb. 28, 2020. Authorities in Italy decided to re-open schools and museums in some of the areas less hard-hit by the coronavirus outbreak in the country which has the most cases outside of Asia, as Italians on Friday yearned for a return to normal life even amid fears that the outbreak could plunge the country's economy into recession. AP Streets of Venice empty due to Coronavirus fears A local pulls a trolley as she leaves a street food market in Venice, Saturday, Feb. 29, 2020. A U.S. government advisory urging Americans to reconsider travel to Italy due to the spread of a new virus is the "final blow" to the nation's tourism industry, the head of Italy's hotel federation said Saturday. Venice, which was nearing recovery in the Carnival season following a tourist lull after record flooding in November, saw bookings drop immediately after regional officials canceled the final two days of celebrations this week, unprecedented in modern times. AP Streets of Venice empty due to Coronavirus fears Locals wait for a mass at the barely empty San Salvador church in Venice, Sunday, March 1, 2020. A coughing Pope Francis told Italy, pilgrims gathered for the traditional Sunday blessing that he is canceling his participation at a week-long spiritual retreat in the Roman countryside because of a cold. It is the first time in his seven-year papacy that he has missed the spiritual exercises that he initiated early in his pontificate to mark the start of each Lenten season. AP Streets of Venice empty due to Coronavirus fears Tourists wearing protective masks take photographs in Venice, Sunday, March 1, 2020. Italian tourism officials are worrying a new virus could do more damage to their industry than the Sept. 11 terror attacks as the country's confirmed cases surpassed 1,000. AP Streets of Venice empty due to Coronavirus fears Tourists wearing protective masks look at their smartphones as they have a break at the St. Mark's square in Venice, Sunday, March 1, 2020. Italian tourism officials are worrying a new virus could do more damage to their industry than the Sept. 11 terror attacks as the country's confirmed cases surpassed 1,000. AP Streets of Venice empty due to Coronavirus fears A couple stand at the Rialto bridge during a rainy day in Venice, Sunday, March 1, 2020. Italian tourism officials are worrying a new virus could do more damage to their industry than the Sept. 11 terror attacks as the country's confirmed cases surpassed 1,000. AP Streets of Venice empty due to Coronavirus fears An empty canal is seen after the spread of coronavirus has caused a decline in the number of tourists in Venice, Italy, March 1, 2020. REUTERS Streets of Venice empty due to Coronavirus fears An empty canal is seen after the spread of coronavirus has caused a decline in the number of tourists in Venice, Italy, March 1, 2020. Reuters Streets of Venice empty due to Coronavirus fears An empty canal is seen after the spread of coronavirus has caused a decline in the number of tourists in Venice, Italy, March 1, 2020. REUTERS Streets of Venice empty due to Coronavirus fears An empty canal is seen after the spread of coronavirus has caused a decline of tourists in Venice, Italy, March 1, 2020. REUTERS Streets of Venice empty due to Coronavirus fears An empty water bus after the spread of coronavirus has caused a decline in the number of tourists in Venice, Italy, March 1, 2020. REUTERS Streets of Venice empty due to Coronavirus fears Tourists shelter against the rain with umbrellas as they walk in the empty St. Mark's Square during a rainy day in Venice, Sunday, March 1, 2020. Italian tourism officials are worrying a new virus could do more damage to their industry than the Sept. 11 terror attacks. AP Streets of Venice empty due to Coronavirus fears Gondolas are parked on a rainy day in Venice, Sunday, March 1, 2020. Italian tourism officials are worrying a new virus could do more damage to their industry than the Sept. 11 terror attacks. AP

“We expect the number of cases to increase in the coming days and weeks,” Jeff Duchin, health officer for the public health agency said at a press conference on Monday. “We are taking this situation extremely seriously.”

He added: “It is impossible for me to predict what that peak of this outbreak (#coronavirus) will be, but our hospitals here locally are already feeling the strain.”

Dow Constantine, the executive of King County, of which Seattle is the largest city, said he had signed an emergency declaration for the county. It was also buying a motel in the Seattle area where people who were infected with coronavirus could stay to remain isolated.

“We have moved to a new stage in the fight to contain and mitigate this outbreak. King County is aligned and organised behind this common mission, with public health – Seattle & King County as our lead agency,” said said Mr “We will direct all available resources to help cities, health-care facilities, businesses, and families continue life as normally as possible. But our best strategies depend on millions of residents actively following established disease prevention guidelines.”

County chair Claudia Balducci said: “As we learn more about this outbreak, it’s now more important than ever that we look out for one another and stand strong as a community.”

The development came as Donald Trump said at White House his administration was talking to pharmaceutical firms and scientists as to whether work on a vaccine could be intensified. Most experts say it is unlikely one could be produced in less than 18 months, at the very minimum.

Officials in Washington state said that 18 cases of the virus had now been confirmed, 14 of them in King County. Of those at least eight were residents of the Life Care Centre, located in the Seattle suburb of Kirkland. Four of the dead had been residents at this facility.

One of the fatalities in Seattle was not a resident at the facility and a sixth death was in Snohomish County, which includes with city of Everett. It was in Everett that officials in January announced the US’s first confirmed case of the disease.

On Sunday night, the International Association of Fire Fighters said 25 members who responded to calls for help at the nursing facility were being quarantined.