By Maria Caspani and Gabriella Borter

NEW YORK (Reuters) -COVID-19 cases surged in New York City and around the United States over the weekend, dashing hopes for a more normal holiday season, resurrecting restrictions and stretching the country’s testing infrastructure ahead of holiday travel and gatherings.

The spike is alarming public health officials, who see the Omicron variant of the coronavirus fast becoming dominant in the United States and fear an explosion of infections after the Christmas and New Year’s holidays.

With the new variant in circulation, COVID-19 cases are now doubling in one and a half to three days in areas with community transmission, the World Health Organization said on Saturday.

Lines for COVID-19 tests wrapped around the block in New York, Washington, D.C., and other U.S. cities over the weekend as people clamored to find out if they were infected before celebrating the holidays with family.

“I just want to make sure before seeing my wife’s 70-year-old mom that I’m negative,” said David Jochnowitz while waiting for a test in Washington.

With a rapid rise in infections, Washington Mayor Muriel Bowser on Monday reinstated an indoor mask mandate until the end of January and required government workers to get vaccinated, including a booster shot.

“I think we’re all tired of it,” Bowser told reporters. “I’m tired of it too, but we have to respond to what’s happening in our city and what’s happening in our nation.”

In New York City, COVID-19 cases rose 60% in the week that ended on Sunday as the Omicron variant spread rapidly around the U.S. northeast. New York has set records for the most new cases reported in a single day since the pandemic started for three consecutive days.

“It is a predictor of what the rest of the country will see soon, and the minimum – since NYC is highly vaccinated – of what other parts of the country will experience in under-vaccinated cities and states,” said Georges Benjamin, executive director for American Public Health Association.

Many Broadway productions canceled performances as cast and crew have become infected. The popular “Hamilton” production on Monday extended cancellations until after Christmas due to breakthrough COVID-19 infections.

Breakthrough infections are rising among the 61% of the country’s fully vaccinated population, including the 30% who have gotten booster shots.

Omicron appears to be causing milder symptoms in vaccinated populations, and health experts remain optimistic this wave might not cause the same spikes in hospitalizations and deaths as previous surges.

‘JUST STAY HOME’

New York City Health Commissioner Dr. Dave Chokshi on Monday said that while new COVID-19 cases have “increased sharply,” hospitalizations have not jumped at the same rate. He credited vaccinations and booster shots, which help prevent severe illness, and urged that more were needed to build a “sea wall” against the variant.

The rise of Omicron prompted Duke University in Durham, North Carolina, on Monday to require all students, faculty and staff to get a COVID-19 booster shot for the upcoming spring semester.

On Monday, Maryland Governor Larry Hogan announced he tested positive for COVID-19. U.S. Senators Cory Booker and Elizabeth Warren said the same on Sunday. All three said they had been vaccinated and boosted.

Nationally, cases rose 9% in the past week but are up 57% since the start of December, according to a Reuters tally. Hospitalized COVID-19 patients have increased 26% this month, with hospitals in some areas already strained by the Delta variant.

While cases climbed in the U.S. Northeast, Midwest hospitals are still dealing with a surge in patients from a Delta wave this fall. Michigan, Indiana and Ohio have the nation’s most hospitalized COVID patients per 100,000 residents, a Reuters tally found.

In New York City, the daily test rate reached an average of 130,000 per day, Mayor Bill de Blasio told reporters on Monday, more than double three weeks ago.

With demand for tests exceeding capacity, de Blasio said the city was working with the White House and private sector to help increase testing availability.

New York Governor Kathy Hochul said on Monday she was ramping up the state’s testing program, with 1 million kits arriving this week and the same amount in each of the next two weeks.

“More and more people are going to be testing positive from this,” she said. For those who do, she advised: “Just stay home, do not go out. Don’t go to work. Don’t go see your family.”

Omicron’s arrival is a headwind for an economic revival in New York that already lags the rest of the country, especially where employment is concerned.

The pandemic delivered an even larger body blow to the city than the country because of the outsized role played by tourism, leisure and hospitality, which suffered the worst under lockdowns and travel restrictions. New York’s jobless rate topped out at 20% in the spring of 2020 – more than 5 percentage points above the U.S. average, and is still 9%, more than twice the national rate.

(Reporting by Maria Caspani in New York, Lisa Shumaker in Chicago; Additional reporting and writing by Gabriella Borter in Washington and Peter Szekely in New York; Additional reporting by Carl O’Donnell in New York and and Greg Savoy in Washington; Editing by Bill Berkrot)