New York's governor announced Tuesday he is sending the National Guard into a New York City suburb to help fight the nation's biggest known cluster of coronavirus cases, as the battle against the U.S. outbreak intensified.

The move — one of the most dramatic steps taken yet to deal with the crisis in the United States — came as health authorities contended with alarming bunches of infections on both coasts and scattered cases in between.

New York Gov. Andrew Cuomo said three schools and other gathering places will be shut down in a containment zone in New Rochelle, the epicenter of an outbreak of more than 100 cases. He said troops will scrub surfaces and deliver food to the zone, which extends a mile in all directions from a synagogue connected to some of the cases.

Residents and visitors to the community of about 79,000 people will still be able to come and go freely, and businesses can remain open.

“It is a dramatic action, but it is the largest cluster of cases in the country,” Cuomo said. “The numbers are going up unabated, and we do need a special public health strategy."

New Rochelle and surrounding Westchester County account for the majority of the state's 173 coronavirus cases. New York City, with 100 times the population of New Rochelle, has 36 known infections.

On other fronts in the battle to stop the virus from spreading, more schools and universities sent students home, conferences and other events were canceled, and the United Nations announced it would close its New York headquarters to the public and suspend all tours.

On Wall Street, stocks surged Tuesday after suffering staggering losses the day before, with the Dow Jones Industrial Average gaining more than 1,100 points on hopes the Trump administration would take steps to cushion the economy from the damage caused by the outbreak.

In Oakland, California, thousands of restless passengers who have been stuck aboard a cruise ship hit by the coronavirus waited their turn to get off the vessel and go to U.S. military bases or back to their home countries for two weeks of quarantine.

“I’m bored and frustrated,” said Carolyn Wright, 63, of Santa Fe, New Mexico. "All of a sudden a two-week vacation has turned into a five-week vacation.”

In Washington state, where at least 19 deaths have been connected to a Seattle-area nursing home, Gov. Jay Inslee announced new nursing-home rules for screening health care workers and limiting visitors.

“If we assume there are 1,000 or more people who have the virus today ... the number of people who are infected will double in five to eight days,” he warned.

In Kentucky, Gov. Andy Beshear said state-run nursing homes will severely restrict visitors, with private operators strongly urged to follow suit. Six cases have been diagnosed in the state.

The virus has infected more than 800 people in the U.S. and killed at least 28, with one state after another recording its first infections in quick succession. New Jersey reported ts first coronavirus death Tuesday. Worldwide, nearly 120,000 have been infected and over 4,200 have died.

For most people, the virus 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. Most people recover in a matter of weeks, as has happened with three-quarters of those infected in mainland China.

A top federal health official pointed to Europe, rather than the virus' point of origin in China, as the likely source for the infection's continued spread to the U.S.

“Right now the epicenter — the new China — is Europe,” Robert Redfield, director of the Centers for Disease Control and Prevention, said on Capitol Hill. “And there’s a lot of people coming back and forth from Europe that are now starting to seed these communities.”

In California, passengers from the coronavirus-stricken Grand Princess were allowed off the vessel and walked to the bottom of a ramp, where masked officials in yellow protective gear and blue plastic gloves took their temperature and led them to a tent for more screening before they lined up to board a bus.

Authorities said foreign passengers would be flown home, while Americans would be flown or bused to military bases in California, Texas and Georgia for testing and 14-day quarantines.

After days of being forced to idle off the Northern California coast, the ship docked Monday at Oakland with about 3,500 passengers and crew, including at least 21 who tested positive for the new virus.

About 1,100 crew members, 19 of whom tested positive for the virus, will be quarantined and treated aboard the ship, which will dock elsewhere after passengers are unloaded, Gov. Gavin Newsom said. He and Oakland's mayor sought to reassure people that no passengers would be exposed to the public before completing quarantine.