Widespread shutdowns, including of schools, come with pledge on tests

The United States began imposing harsher measures to contain the spread of the novel coronavirus as cases numbers rise sharply, with 3,774 confirmed infections and 69 fatalities as of Sunday night, according to a tally by Johns Hopkins University.

Thousands of schools, from kindergartners to universities, will be closed nationwide. Stores and supermarkets were curbing hours or shutting down altogether. Cities and states were recommending or requiring mass closures of other stores and public places, and even self-isolation by residents on a massive scale.

The US Centers for Disease Control on Sunday issued further guidance, encouraging social distancing and recommending against gatherings of 50 or more people for the "next eight weeks".

At a Sunday evening news briefing at the White House, health officials said they are planning to ramp up virus testing by tens of thousands of additional people a week, beginning this week.

As the virus spreads, US citizens are waking up to a new reality, with store shelves stripped bare of essentials, schools closed and millions of jobs in jeopardy as businesses temporarily shut their doors.

President Donald Trump urged US citizens to "relax" and stop buying more groceries than they need.

"You don't have to buy so much," Trump said at a Sunday news conference. "We're learning from watching other countries. It's a very contagious virus ... but it's something that we have tremendous control of."

Trump assured US citizens, after speaking with leading grocery chain executives, that grocers would remain open and that the supply chain remained healthy. Speaking at the same White House news conference, Vice-President Mike Pence urged people to buy only the groceries they need for the week ahead.

Trump himself has tested negative for coronavirus, his doctors said on Saturday, as the president extended a travel ban to the United Kingdom and Ireland in a bid to slow the pandemic.

The president's spokesman, Judd Deere, said temperature checks will be conducted on everyone who enters the White House grounds, beginning on Monday morning.

Travelers returning to the US and being screened for the novel coronavirus were met by long lines and massive delays at some major airports, prompting federal officials to deploy more staff.

Pence said the government on Monday would issue updated federal guidelines, which he described as "broad-based recommendations for the American public".

In drastic measures, New York Mayor Bill de Blasio said the city's usually buzzing bars and restaurants would be restricted to takeout or delivery, and that nightclubs, theaters and concert venues must close starting on Tuesday.

Schools, museums and sports arenas have already closed in many US states－but lively St Patrick's Day celebrations were still held despite pleas to limit socializing, prompting calls for more aggressive action.

"Our city is facing an unprecedented threat, and we must respond with a wartime mentality," De Blasio said in a statement.

A clinical trial to evaluate a vaccine designed to protect against the novel coronavirus will begin on Monday, and it would take a year to 18 months to fully validate any potential vaccine, The Associated Press reported, citing an unnamed US government official.

Virus in Latin America

Apart from the US, Latin America has also tightened its measures to suppress the novel coronavirus outbreak. Chile has suspended classes at the elementary, secondary and university levels in Santiago and 20 other cities.

Argentine President Alberto Fernandez has announced his government will suspend classes and close the borders for 15 days.

In Mexico, education authorities announced they were prolonging the two-week Holy Week holiday to four weeks, meaning some 250,000 public schools and universities will close from March 20 to April 17.

Peruvian President Martin Vizcarra declared on Sunday a state of emergency, ordering borders to be closed and people to stay home, while Honduras closed its borders from 11:59 pm on Sunday and ordered the suspension of most businesses.

Xinhua and agencies contributed to this story.