NEW YORK -- The coronavirus outbreak could kill 100,000 to 200,000 Americans, the U.S. government's top infectious-disease expert warned on Sunday as family members described wrenching farewells through hospital windows with dying loved ones.

Faced with that grim projection and the possibility even more could die in the U.S. without measures to keep people away from one another, President Donald Trump extended federal guidelines recommending people stay home for another 30 days until the end of April to prevent the spread of the virus.

Trump's extension of the original 15-day guidelines was a stark reversal just days after he said he hoped the economy could restart in about two weeks and came after Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, made the dire prediction of fatalities, adding that millions in the U.S. could become infected.

By We want to make sure that we don't prematurely think we're doing so great," Fauci said of the extension of the federal guidelines.

By Sunday night, the U.S. had over 140,000 infections and 2,400 deaths, according to the running tally kept by Johns Hopkins University, though the true number of cases is thought to be considerably higher because of testing shortages and mild illnesses that have gone unreported.

Worldwide, more than 720,000 infections were reported, and deaths topped 33,000, half of them in Italy and Spain, where the health system is at the breaking point.

New York state -- where the death toll passed 1,000 -- remained the epicenter of the U.S. outbreak, with the vast majority of the deaths in New York City. But spikes in infections were recorded around the country, not only in metropolitan areas but in Midwestern towns and Rocky Mountain ski havens. West Virginia reported its first death, leaving only two states -- Hawaii and Wyoming -- with none linked to the outbreak.

The virus is moving fast through nursing homes, assisted living facilities and other places that house elderly or otherwise vulnerable people, spreading "like fire through dry grass," New York Gov. Andrew Cuomo said.

Since the U.S. saw its first major outbreak of the coronavirus earlier this month -- centred at a nursing home in Kirkland, Washington -- a stream of similar facilities have battled infections among residents and staff.

A week ago, the Centers for Disease Control and Prevention said 147 nursing homes in 27 states had patients with COVID-19. The problem has only worsened since.

In Woodbridge, New Jersey, a nursing home relocated all of its residents after two dozen were confirmed infected and the rest were presumed to be. In Louisiana, at least 11 nursing homes, largely in the New Orleans area, have reported cases. In Mount Airy, Maryland, a death linked to the virus was recorded in a home where 66 people were confirmed infected.

Residents' loved ones are being kept away to try to slow the spread.

Willa Robinson, whose husband, Vernon, died Thursday, said she last saw him healthy on March 13 -- the day before his nursing home in Burbank, California, prohibited visitors. She brought him his favourite meal of baked chicken, garlic mashed potatoes and carrots and left with their customary farewell.

"I love you," she told him. "I love you more," he replied.

She sat outside his hospital room days ago and watched through a glass window as he struggled to breathe. Now she must mourn her husband of 55 years in isolation.

"Nobody can come to me," she said.

Others feared they may get no goodbye.

"I have a feeling that I very likely may never see my mother again," said James Preller, whose 94-year-old mother, Ann Preller, is a resident at Peconic Landing, a retirement community on New York's Long Island where seven have died recently.

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

In New York, the virus is overwhelming some of the city's poorest neighbourhoods, with data showing high rates of infection in densely packed areas with big non-English-speaking populations.

Dr. Craig Smith, who heads the surgery department at New York-Presbyterian/Columbia University Medical Center, said the hospital will probably be forced into "apocalyptic scenarios" in the coming weeks in which ventilators and intensive care unit beds will need to be rationed.

Trump spoke of the haunting images he had seen on television this week of bodies being removed from Elmhurst Hospital in his native Queens and put in large refrigerated trucks.

"Body bags all over, in hallways," Trump said. "I've seen things that I've never seen before."

New York City Mayor Bill De Blasio asked the federal government to deliver 400 more ventilators and warned that the city will run out of masks, gowns and other supplies in a week if they don't get reinforcements.

Worry for the poorest was being echoed around the world.

In India, a lockdown covering the country's 1.3 billion people has put untold numbers out of work and left many families struggling to feed themselves. Tens of thousands in New Delhi were forced to flee their homes, with no way to pay the rent, journeying back to their native villages. Women in saris held babies on their hips. Others toted their belongings in bags normally used for cement.

Prime Minister Narendra Modi apologized for the hardships but said, "These tough measures were needed to win this battle."

Though the U.S. leads the world in reported cases, five other countries have higher death tolls: Italy, Spain, China, Iran and France.

Italy reported more than 750 new fatalities Sunday, bringing the country's total to nearly 10,800. But the number of new infections showed signs of easing, with officials expressing cautious optimism that the most severe shutdown in the industrialized West is showing results.

Italy's civil protection agency said more than 5,200 new cases were recorded in the last 24 hours, the lowest number in four days, for a total of almost 98,000 infections.

Spain moved to tighten its lockdown and ban all nonessential work as it hit another daily record of almost 840 dead. The country's overall official toll was more than 6,500.

Egypt shut its beaches as cases in the Mideast surpassed 50,000. Police in the Philippines stepped up arrests of quarantine violators, and more tourists were evacuated from Mount Everest and the Indonesian island of Bali.

Russia ordered borders to close on Monday, Moscow all but confined its 12 million residents to their homes, and the head of the Russian Orthodox called on believers to stay away from churches and pray at home instead.

A prominent French politician with the virus died, the country's first death of a senior official.

Restrictions that would have been unthinkable weeks ago have been imposed in Europe and elsewhere. Parisians are fined if they try to leave the city, South Africans can't buy liquor, and Serbians are upset over a ban on walking their dogs. In Italy, burials are being held with only one family member.

Some U.S. states began to try to limit exposure from visitors from harder-hit areas. Rhode Island National Guard troops went door to door in coastal communities to find New Yorkers. Florida is setting up checkpoints to screen visitors from Louisiana. Texas said it would require drivers from Louisiana to self-isolate for two weeks.

As others tightened controls, China continued to ease its restrictions: Flights from Hubei province at the epicenter of the country's outbreak resumed Sunday.

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Sedensky reported from Philadelphia. Dazio reported from Los Angeles. Contributing to this report were Associated Press writers Joseph Wilson in Madrid; Colleen Barry in Milan; Angela Charlton in Paris; Joe McDonald in Beijing; Geir Moulson in Berlin; Vanessa Gera in Warsaw; Jacquelyn Martin in Mount Airy, Maryland; Jonathan Drew in Durham, North Carolina; and Marina Villeneuve in Albany, New York.

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This story has been updated to correct that Hawaii and Wyoming are the only remaining states with no reported deaths linked to the coronavirus, not Hawaii and Montana.

Correction:

This story has been updated to correct that Peconic Landing is near Greenport on Long Island, not Green Point.