ST. PETERSBURG, Fla. (AP) — Florida and other states across the Sunbelt are thinning out the deck chairs, turning over the barstools and rushing to line up more hospital beds as they head into the height of the summer season amid a startling surge in confirmed cases of the coronavirus.

With newly reported infections running at around 40,000 a day in the U.S., Dr. Anthony Fauci, the nation's top infectious-disease expert, warned on Tuesday that the number could rocket to 100,000 if Americans don't start following public health recommendations.

Over the past few days, states such as Florida, Arizona, Texas and California have reversed course, closing or otherwise clamping down on bars, shutting beaches, rolling back restaurant capacity, putting limits on crowds at pools, or taking other steps to curb a scourge that may be thriving because of such factors as air conditioning and resistance to wearing masks.

"Any time you have these reopenings, you're depending on people to do the right things, to follow the rules. I think that's where the weak spots come in," said Dr. Cindy Prins, a University of Florida epidemiologist. She warned that things are likely to get worse before they get better.

Hospitals in the new hot spots are already stretched nearly to the limit and are scrambling to add intensive care unit beds for an expected surge in COVID-19 cases in the coming weeks.

Newly confirmed cases in Florida have spiked over the past week, especially in younger people, who may be more likely to survive the virus but can spread it to the Sunshine State's many vulnerable older residents.

The state on Tuesday reported more than 6,000 new cases. More than 8,000 were recorded on each of three days late last week. Deaths have climbed past 3,500. Floridians ages 15 to 34 now make up 31% of all cases, up from 25% in early June. Last week, more than 8,000 new cases were reported in that age group, compared with about 2,000 among people 55 to 64 years old.

Hospital ICUs are starting to fill up in South Florida, with a steadily increasing number of patients requiring ventilators. Miami's Baptist Hospital had only six of its 82 ICU beds available, officials said.

Hard-hit Arizona, where Republican Gov. Doug Ducey shut down bars, movie theaters and gyms and banned groups larger than 10 at swimming pools, has called on hospitals to add more beds.

Air conditioning could be a factor in hot-weather states where new cases have been spiking, because it recirculates air instead of bringing it in fresh from outside, said Dr. Kristin Englund, an infectious-disease physician at Cleveland Clinic.

"I definitely think the air conditioning and the oppressive heat in the South is going to play a role in this," she said.

The coronavirus has been blamed for over a half-million deaths worldwide, including about 130,000 in the U.S., where the number of new cases per day has soared over the past month, primarily in the South and West.

"I would not be surprised if we go up to to 100,000 a day if this does not turn around, and so I am very concerned," Fauci said on Capitol Hill.

Van Johnson, mayor of the tourism-dependent city of Savannah, Georgia, population 145,000, announced he is requiring the wearing of masks, with violators subject to $500 fines.

Savannah becomes one of the first cities in Georgia to take such a step. Republican Gov. Brian Kemp has largely prohibited local governments from imposing rules stricter than the state's.

The new round of shutdowns around the country is likely to cause another spike in layoffs.

Nikki Forsberg said she is relying on government loans to keep afloat the Old Ironhorse Saloon, the only bar in the Texas Hill Country town of Blanco, after it was closed for two months beginning in mid-March and then shut down again on Friday by the governor's order.

She said money got so tight for some of her eight employees during the first shutdown that she told them to go the bar and take whatever they needed — petty cash, toilet paper, even one of the refrigerators.

"That's how desperate it got," she said. "By the time we had opened back up, we had stripped the bar of all the non-liquor inventory."

Health officials say the next several weeks will be critical in Florida. The Fourth of July, the reopening of Walt Disney World on July 11, and the Republican National Convention in Jacksonville at the end of August promise to draw crowds and create the potential for person-to-person spread.

While cities like Miami, Fort Lauderdale, St. Petersburg and Sarasota have mandated masks, some people in Florida have been resistant.

Zoe Mitchell wasn't wearing a mask as she tucked into a salad in St. Petersburg. The 26-year-old bartender said that if people are worried, "they should stay home."

In The Villages retirement community near Orlando, tension has developed among residents who wear masks and those who don't. And the split has been along political lines.

Ira Friedman, who along with wife, Ellen, is active in the local Democratic Party, said that at first, he would just make an exaggerated cough to get his point across if he saw someone without a mask. But he said he has become more vocal about it as the number of cases has grown.

"Unfortunately, we don't find that the Republicans are following the same protocols as we are," his wife said.

Elsewhere, the European Union will reopen on Wednesday to visitors from 14 countries — but not the U.S., which has barred most Europeans. The EU also kept its ban in place for visitors from China and from countries such as Russia, Brazil and India where infections are running high.

Americans make up a big share of Europe's tourism industry, and summer is a key period. More than 15 million Americans travel to Europe each year, while some 10 million Europeans head across the Atlantic.

"Americans were 50% of my clientele," lamented Paola Pellizzari, who owns a mask and jewelry shop on the Saint-Louis island in the heart of Paris and heads its business association. "We can't substitute that clientele with another."

Across the English Channel, things are also headed in reverse in places.

Britain reimposed a lockdown in Leicester, a city of 330,000 people that officials said accounted for 10% of all new coronavirus cases in the nation last week. Stores closed their doors, and schools prepared to send children home.

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Seewer reported from Toledo, Ohio. Associated Press reporters from around the world contributed to this report.