Up to 70 million people in the US will be put on lockdown as America tries to come to grips with the coronavirus crisis.
California, America’s largest state with a population of around 40 million people, was put on lockdown on Friday, while officials in New York and Illinois announced they will largely restrict residents to their homes this weekend.
American hospitals are already feeling the strain of Covid-19 and officials are desperate to prevent a repeat of what has happened in large parts of China, Italy and Spain, where the outbreak has overwhelmed emergency services.
It comes as US President Donald Trump gave businesses extra time to file their taxes, giving them to July 15 instead of April 15. He said the decision would being no added penalties for companies, calling it "a big deal".
The US president added: "Every American has a role to play in defending our nation from this invisible, horrible enemy.
"It really is an invisible enemy - and we will be successful, hopefully very much sooner than people would think.
"So we say stay at home and save lives. It is a time of shared national sacrifice but it's also a time to treasure our loved ones and to take stock of what is most important; our faith, our families, our neighbours and our great country.
"I want to thank all of the incredible people, the citizens of our country."
He said the way people have been responding has been "very special" and would not be forgotten by history, by declaring the US would be "celebrating a great victory in the not too distant future".
More than 275,000 cases have been confirmed globally, including more than 11,000 deaths, according to a running tally by Johns Hopkins University. Nearly 90,000 have recovered.
In the US, restrictions are set to be imposed in Illinois on Saturday, with New York following suit on Sunday. Connecticut and Oregon are preparing similar moves.
New York authorities said all workers in non-essential business will be required to stay at home and gatherings of any size will be banned. Residents will be allowed out to buy food, medicine and exercise.
The lock-downs in California and other states sent stock markets tumbling again. Wall Street had its worst week since the 2008 financial crisis, with the Dow Jones Industrial Average falling more than 900 points and down 17 per cent for the week.
The White House said a member of Vice President Mike Pence’s staff has tested positive for the coronavirus. A spokeswoman said the person did not have close contact with either Pence or President Donald Trump.
In the UK, prime minister Boris Johnson announced that pubs, clubs, restaurants and gyms would be closed indefinitely.
Across Europe, other countries have imposed more stringent measures, with Italy, Spain and France being put on virtual lockdowns.
Elsewhere, Colombia became the latest country in South America to announce a lock-down, following Peru, Ecuador and Venezuela.
President Ivan Duque announced on Friday night that Colombians will be required to isolate in their homes from Tuesday until April 13. The capital Bogota began its own lock-down on Friday, leaving the city’s usually traffic-filled streets largely empty.
The country has 158 confirmed cases, and officials are hoping that drastic measures now will limit the number of new cases in the weeks ahead.
China - the original epicentre of the outbreak - reported that the mainland had no new home-grown cases of the disease for the third day in a row, but there had been 41 imported cases.
Coronavirus: Everything you need to know