WASHINGTON (AP) —

President Donald Trump announced Saturday that the United States will expand its European travel restrictions to include Britain and Ireland as the U.S., armed with new tools against the pandemic, braced for it to get worse before it gets better. The government's top infection expert warned that COVID-19 may surge within the nation in coming days.

Under the restrictions on European travel, American citizens, green card holders and others are still allowed to return home to the U.S., but will be funneled to 13 airports and be subjected to health screenings and quarantine orders.

“If you don't have to travel, I wouldn't do it," Trump said.

Trump also said he had taken the coronavirus test following several interactions with people who are infected. Hours later, the White House announced that the president's test was negative.

The White House also began testing the temperatures of everyone who's been close to Trump; he told reporters that his own temperature was normal and he was feeling fine.

The House approved legislation early Saturday to provide direct relief to Americans suffering physically, financially and emotionally from the coronavirus pandemic. The Senate still must vote on the package. Trump supports it. As well, he declared a national emergency Friday, unleashing as much as $50 billion for state and local governments to respond to the crisis.

There was little hope of a quick turnaround.

“We will see more cases and we will see more suffering and death," said Dr. Anthony Fauci of the National Institutes of Health, “particularly among the vulnerables." Yet he said “we still have opportunities” to lessen the severity of the pandemic. The U.S. has recorded at least 51 deaths and nearly 2,500 confirmed infections.

For most people, COVID-19 causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia.

The vast majority of people recover. According to the World Health Organization, people with mild illness recover in about two weeks, while those with more severe illness may take three to six weeks to be over it.

The new travel restrictions come as Britain has seen its death toll from the virus nearly double from the day before to 21, and the number of people infected rise to over 1,100 from about 800 the previous day. Ireland had 90 confirmed cases and one death by Friday.

The U.S. said earlier in the week a 30-day restriction on flights covered only the 26-nation Schengen area, the European Union’s border-free travel zone, which excludes Britain and Ireland. Vice President Mike Pence said the restrictions on Britain and Ireland would go into effect midnight on Monday night.

Pence added that federal officials were “considering a broad range of measures” for potential domestic travel restrictions but no decisions have been made. “We're going to continue to follow the facts,” Pence said.

But a senior homeland security official, in a briefing held on condition that the official not be identified, said "there’s no expectation of any domestic travel restrictions at this time” by air or rail.

Britain has taken a different approach as countries across Europe and other afflicted areas have shut schools, scrapped large public events and shuttered bars and restaurants. The British government hasn’t heavily restricted everyday activities, though there were indications it might.

Schools in Northern Ireland were operating as usual but across the border in the Irish Republic, schools, colleges, daycare centers and cultural institutions were closed.

In the U.S., Senate Majority Leader Mitch McConnell canceled the coming week’s planned recess to deal with the matter. Senate Democrats called on McConnell, who let senators leave town for the weekend, to reconvene now and pass the aid package.

“Everyone is going to have new ideas, but that will slow things down,” said Sen. Chuck Schumer, the top Senate Democrat. “We have to act immediately.” With the president’s backing and robust Republican support from the House vote, passage appears likely..

While anxiety hangs over the nation, the president took a lighter tone at moments as he addressed the media. He boasted that he was “honored” that the Dow Jones Industrial Average reacted with a huge one-day gain Friday after he announced the national emergency declaration.

“I think we should do one of them every day perhaps," joked Trump, who wore a blue baseball cap emblazoned with “USA." “How about five times a day?"

The president didn't mention that despite Friday's pickup, the market had its worst week since October 2008. In just a few weeks, U.S. stocks have lost all the gains made during 2019.

The crush of activity capped a tumultuous week in Washington as the fast-moving virus left ordinary Americans suddenly navigating self-quarantines, school closures and a changed way of life.

Trump took a number of other actions to bolster energy markets, ease the financial burden for Americans with student loans and give medical professionals additional flexibility in treating patients during the public health crisis.

Central to the aid package from Congress, which builds on an emergency $8.3 billion measure approved earlier, are the free testing, sick pay and family leave provisions.

Providing sick pay for workers is a crucial element of federal efforts to stop the rapid spread of the infection. Officials warn that the nation’s healthcare system could quickly become overwhelmed with gravely sick patients, as suddenly happened in Italy, one of the countries hardest hit by the virus.

The ability to ensure paychecks will keep flowing — for people self-quarantining or caring for others — can help assure Americans they will not fall into financial hardship. The legislation also offers three months of paid family and medical leave. Small and mid-sized employers will be reimbursed through tax credits.

Both Treasury Secretary Mnuchin and House Speaker Nancy Pelosi promised a third coronavirus package will follow soon, with more aggressive steps to boost the U.S. economy, which economists fear has already slipped into recession.

Mnuchin said Saturday that lawmakers will have to fix a minor error in the approved House bill, which could create some hiccups in getting the measure to Trump's desk by early in the week. It involves a delicately negotiated provision about a tax credit for businesses to provide sick leave.

Trump on Friday also told people to expect the imminent rollout of a website "facilitated” by Google that would guide users through a series of questions to determine whether they should be screened for the virus. If testing is recommended, users would be directed to a local testing location, which could include parking lots at Walmart, Target, Walgreens and other chains.

But it quickly became apparent that such a fast track to testing was in early stages of development and would not be widely employed soon.

Meantime U.S. officials said most cruise companies had stopped new voyages and the few that hadn't were ordered to. Trump endorsed decisions some companies have taken to close their stores as the nation increasingly hunkers down.

The Pentagon and State Department announced new guidance aimed at limiting movement of its personnel and promoting social distancing in hopes of reducing the impact of the pandemic on the agencies. As part of that, State Department employees were to engage in “mission critical” travel only.

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Associated Press writers Jill Colvin, Lisa Mascaro and Andrew Taylor contributed reporting to this article.

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The Associated Press receives support for health and science coverage from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.