“I am confident that by counting and continuing to take these tough measures we will significantly reduce the threat to our citizens and we will ultimately and expeditiously defeat this virus,” President Donald Trump said Wednesday evening, announcing a 30-day ban on certain travel from Europe.

But domestically, the administration has been slow to issue specific guidance or declare a nationwide state of emergency, leaving governors, mayors and other local officials to implement a patchwork of guidelines and rulings that vary from state to state. The Trump team’s response has been the subject of steady criticism in recent weeks amid its struggles to ramp up testing and rhetorical misfires from the president, who spent weeks downplaying the economic and public health threats posed by the virus’ spread.

Futures markets immediately swooned, and trading was temporarily halted Thursday morning as investors fled to safety and stock indexes plunged. The Dow Jones Industrial Average plummeted more than 2,000 points, or 10 percent, by the close of trading, marking its worst percentage drop since the 1987 crash.

Trump told reporters Thursday morning that he hadn’t discussed placing travel restrictions inside the U.S. in states like Washington and California — where 34 combined deaths have occurred — but that it was a possibility “if somebody gets a little bit out of control” or if “an area gets too hot.”

“You see what they’re doing in New Rochelle, which is good, frankly,” the president said, referring to the city in which New York Gov. Andrew Cuomo implemented a special “containment area” to manage the outbreak. “It’s the right thing, but it’s not enforced. It’s not very strong, but people know they’re being watched. New Rochelle, that’s a hot spot.”

House Speaker Nancy Pelosi (D-Calif.) told reporters that it’s “kind of shocking to see the challenges that we have and the decisions that have to be made about people coming together.”

Even the typically laconic Senate majority leader, Mitch McConnell, felt compelled to acknowledge the widespread sense of alarm radiating outward from Washington and New York. The Kentucky Republican canceled the upcoming weeklong recess in the upper chamber so “Congress can pass bipartisan legislation to continue combating the coronavirus and keep our economy strong.”

“This virus is challenging our nation in ways that feel unfamiliar to us,” he said in an earlier statement. “But our great country is strong, we are equipped, and we have overcome far greater challenges before.”

What began as health officials stressing the importance of washing hands and avoiding handshakes now includes government action against large crowds across the country as the nation races to mitigate the spread of the virus.

In California, Gov. Gavin Newsom has recommended the cancellation of any gatherings of more than 250 people across the state through the end of the month, following the lead of Washington Gov. Jay Inslee, who announced a similar ban Wednesday in three counties. Most K-12 schools wil. remain open in California, but Disneyland Resort and Disney California Adventure will close Saturday until the end of the month. (The Walt Disney Co. later said it would also shut down Disney World in Orlando, Fla., and Disneyland Paris beginning Sunday night until the end of March.)

New Mexico, New York and New Jersey are temporarily barring mass gatherings, while Oregon is banning mass gatherings for organized events for the next month.

After nearly every Division I conference canceled its postseason basketball tournament, the NCAA announced the cancellation of its national men’s and women’s basketball championship tournaments in addition to its remaining winter and spring championships.

The remainder of the NBA’s regular season won’t be played, at least for the time being, after the league announced that a member of the Utah Jazz roster tested positive for coronavirus Wednesday. A second Jazz player tested positive Thursday.

The WNBA is not in season, but with its draft a month away and the start of the regular season set for May 15, the league said it will continue planning for different scenarios and release further details later this month.

The seating area at Bankers Life Fieldhouse in Indianapolis. The Big Ten Conference announced that the remainder of the men's NCAA college basketball games tournament was cancelled. | Michael Conroy/AP Photo

Major League Soccer and the National Hockey League have suspended play, while NASCAR and the PGA Tour will continue without fans in attendance. Major League Baseball will delay its opening day by at least two weeks. And next month’s annual Boston Marathon will be postponed.

The State Department has urged Americans to reconsider their travel plans and paused its international exchange programs, while the Pentagon has shut down tours of the Defense Department. Meanwhile, the House and Senate sergeant at arms on Thursday announced the temporary closure of all public tours of the Capitol complex through the end of March.

“We are taking this temporary action out of concern for the health and safety of congressional employees as well as the public,” House Sergeant at Arms Paul Irving and Senate Sergeant at Arms Michael Stenger said in a joint statement. “We appreciate the understanding of those with planned visits interrupted by this necessary, but prudent, decision.”

The shutdowns, postponements and cancellations are likely to trigger more of the same from companies, campaigns and others as top health officials warn that the coronavirus outbreak will get worse.

The House Oversight Committee resumed a hearing Thursday with Robert Redfield, director of the Centers for Disease Control and Prevention, and Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, that was postponed Wednesday due to an “emergency” White House meeting with President Donald Trump and Vice President Mike Pence.

But even a member of the committee argued that it should have been canceled or postponed.

“These gentlemen should be able to go and do their work,” Rep. Clay Higgins (R-La.) said. “There’s a time and battle when you need your frontline men on the front line, not in the rear with the gear.”

Fauci told lawmakers that America’s test system “is failing,” noting that it’s not set up for mass testing like other countries.