NEW ORLEANS >> New Orleans rushed to build a makeshift hospital in its convention center today as troubling new outbreaks bubbled in the United States, deaths surged in Italy and Spain and the world warily trudged through the pandemic that has sickened more than a half-million people.

Punctuating the fact that no one is immune to the new coronavirus, it pierced even the highest echelons of global power, with British Prime Minister Boris Johnson becoming the first leader of a major country to test positive.

While New York remained the worst hit in the U.S., Americans braced for worsening conditions elsewhere, with worrisome infection numbers being reported in cities including New Orleans, Chicago and Detroit.

“We are not through this. We’re not even half-way through this,” said Joseph Kanter of the Louisiana Department of Health, which has recorded more than 2,700 cases, more than five times what it had a week ago.

New Orleans’ sprawling Ernest N. Morial Convention Center, along the Mississippi River, was being converted into a massive hospital as officials prepared for thousands more patients than they could accommodate. The preparations immediately conjured images of another disaster, Hurricane Katrina in 2005, when the convention center became a squalid shelter of last resort in a city that has braved a string of storm hits, not to mention great fires and a yellow fever epidemic in centuries past.

As the new health crisis loomed, economic catastrophe had already arrived in the city, where many already live in poverty and the tourism industry has screeched to a halt.

“I’ve never been unemployed. But now, all of a sudden: Wop!” said John Moore, the musician best known as Deacon John, who has no gigs to perform with much of the city shut down. “It ain’t just me. It’s everybody.”

Italy recorded its single biggest rise in deaths, with 969 more victims, to bring its total number of fatalities to 9,134. The country now has 86,498 cases, surpassing China to record the grim distinction of the second-most infections in the world, behind the U.S.

Italian epidemiologists warn that the country’s number of cases is likely much higher than reported — perhaps by five times — although two weeks into a nationwide lockdown the daily increase seems to be slowing, at least in northern Italy.

“It’s a horrible sensation, not being able to breathe,” said Fausto Russo, a 38-year-old fitness trainer who is one of 10,000 Italians whose infection has been cured. “Imagine putting your head under water.”

Spain’s Health Ministry reported another 7,800 infections for a total of 64,059. Deaths climbed by 769 to 4,858 — the world’s second-highest total after Italy’s 8,214 fatalities.

Spain says 9,444 health workers have contracted the coronavirus. That’s nearly 15% of the total number of cases.

“It’s true that we have more deaths than what we saw yesterday, but it’s also true that the percentage increase today is similar to that of the past three days and it appears there is a stabilization,” said Fernando Simón, the head of Spain’s health emergency coordination center.

The British prime minister’s office said Johnson was tested after showing mild symptoms for the coronavirus and that he is self-isolating and continuing to lead Britain’s response to the pandemic.

“Be in no doubt that I can continue, thanks to the wizardry of modern technology, to communicate with all my top team, to lead the national fightback against coronavirus,” Johnson said in a video message, adding that he had a temperature and persistent cough.

Several weeks ago, Johnson had pledged he would “go on shaking hands with everybody.”

Johnson, 55, was the first leader of a major nation known to have contracted COVID-19; German Chancellor Angela Merkel has been in isolation since her doctor tested positive for the virus, but her first two tests have been negative.

Earlier this week Britain’s Prince Charles said he had tested positive.

British Health Secretary Matt Hancock, who has been at the forefront of the nation’s response to the outbreak, also was confirmed to have the virus. Britain has 11,658 confirmed cases and 578 people have died.

In Washington, the House rushed a $2.2 trillion recovery package to President Donald Trump, approving the sweeping measure by voice vote. Lawmakers in both parties lined up behind the measure to send checks to millions of Americans, boost unemployment benefits, help businesses and toss a life preserver to an overwhelmed health care system.

The U.S. now has 85,996 confirmed cases, according to a count kept by Johns Hopkins University. Italy, the U.S.. and China account for nearly half the world’s more than 575,000 infections and more than half of the roughly 26,000 reported virus deaths.

Analysts warned that all those infection figures could be low for reasons that varied in each nation.

“China numbers can’t be trusted because the government lies,” American political scientist Ian Bremmer, president of the Eurasia Group think-tank, said in a tweet. “U.S. numbers can’t be trusted because the government can’t produce enough tests.”

For most people, the coronavirus causes mild or moderate symptoms, such as fever and cough that clear up in two to three weeks. But for others, especially older adults and people with existing health problems, the virus can cause more severe illness, including pneumonia and death.

Johns Hopkins reported more than 128,000 people have recovered, about half in China.

New York state, the epicenter of the U.S. outbreak, reported 100 more deaths in one day, accounting for almost 30% of the 1,300 fatalities nationwide. Gov. Andrew Cuomo said the number of deaths will increase soon as critically ill patients who have been on ventilators for days succumb.

“That is a situation where people just deteriorate over time,” Cuomo said.

Around the world, the pandemic threatened people living in places with little means to respond.

India launched a massive program to feed hungry day laborers after a lockdown of the country’s 1.3 billion people put them out of work. Iran’s military hurriedly finished a 2,000-bed field hospital to accommodate the worst outbreak in the Mideast. In Indonesia, Saudi Arabia, Indonesia, South Africa and elsewhere, the count of the infected passed 1,000 people and worries persisted that it would only get worse.

In China, where the virus was first believed to have started, the National Health Commission today reported 55 new cases, 54 of them imported infections. Once again, there were no new cases reported in Wuhan, the provincial capital where the coronavirus first emerged in December. China is barring most foreigners from entering.

In a phone call today, Chinese leader Xi Jinping told Trump that China “understands the United States’ current predicament over the COVID-19 outbreak and stands ready to provide support within its capacity,” the official Xinhua News Agency reported.

Trump, who has repeatedly referred to the outbreak as a “Chinese virus,” struck a different tone today, tweeting after the call that “China has been through much & has developed a strong understanding of the Virus. We are working closely together. Much respect!”

Beijing has strongly protested U.S. Secretary of State Mike Pompeo’s repeated references to the outbreak as the “Wuhan Flu,” saying that promotes bias against China and Chinese Americans.

Shares skidded early today in Europe after a mixed day in Asia, where Tokyo’s Nikkei 225 jumped while Australia’s benchmark sank 5%. On Wall Street, major indexes were down about 3%, giving up some of the gains the market had piled up over the previous three days.

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Sedensky reported from Philadelphia and Rising reported from Berlin. Associated Press journalists around the world contributed.