NEW YORK (CBSNewYork) -- As the Omicron variant spreads, with at least 10 confirmed cases in the Tri-State Area, new rules are in effect for international travelers.
As of midnight Monday morning, the COVID testing window just got shorter for anyone coming to the United States.
As CBS2's Jenna DeAngelis reports, travelers are touching down at John F. Kennedy International Airport to tighter testing requirements.
"I think it's very important," one Brooklyn man said.
He said he got tested Sunday before flying back from Brazil.
"Everything was very smooth and easy," he said. "I felt very safe. I'm triple vaccinated."
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Regardless of vaccination or nationality, all travelers entering the U.S. must provide proof of a negative test within one calendar day of their flight.
"My PCR test 24 hours before the flight," said Brazil resident Ana Pinto.
"And did they check it in the airport? How did it work?" DeAngelis asked.
"Not here. They check only on check in, in Brazil," Pinto said. "The airline checked it."
Those DeAngelis spoke to at JFK say they had no issues, but across the pond, there was some confusion after the CDC reduced the testing window from 72 hours before departure to 24 hours.
"We found out just randomly, so now we're like, well, do we wait? Do we do our test today? Do we do it tomorrow?" Paul and Laurie from West Orange, N.J. said.
"Same day results is more expensive," another traveler said.
"Definitely another challenge that's coming up in the way for travel," international traveler Zohaib Valani said at John F. Kennedy International Airport.
"That's not going to stop me from traveling," another traveler added.
"It's adding a lot more stress, especially, you know, for those traveling for business, like me," said Mohammad Almadani.
The tightened restriction come as the Omicron variant continues to spread. New York now has at least eight confirmed cases. New Jersey and Connecticut each have one. Some have been tracked to a convention at New York's Javits Center.
"At this point, Omicron is here. It looks like it's very transmissible. That's just going to make a tough situation, even harder," Mayor Bill de Blasio said.
"I'm concerned. Look, Omicron is coming up from New York on the I-95 corridor. But Delta is coming down from New Hampshire, Vermont, Massachusetts. And no state is an island, and no country is an island," Gov. Ned Lamont told "Face the Nation."
"We've got to be careful before we make any determinations that it is less severe or really doesn't cause any severe illness comparable to Delta," said Dr. Anthony Fauci. "But thus far, the signals are a bit encouraging regarding the severity."
A Hoboken resident named Nate says he still plans to fly to Mexico next week for his best friend's wedding and is supportive of the new travel rules.
"It's all going back to staying safe, I would say, slowing the spread of the Omicron," he said.
Along with the testing requirement, President Joe Biden has extended the federal mask mandate at the airport and on public transportation through March 18.
These travel changes are in addition to restrictions imposed on South Africa and seven other countries last month.
"The big question is whether or not Omicron will outcompete Delta. Remember, Delta is dominant, and that's an extremely dangerous variant," said Dr. Maria Van Kerkhove, a World Health Organization infectious disease epidemiologist.
The World Health Organization says initial reports suggest people with Omicron tend to have mild symptoms, but it's too early to tell.
As scientists rapidly study the strain, there's a call for more research and preparation.
At NYU Langone on Sunday, Sen. Kirsten Gillibrand and Rep. Carolyn Maloney joined doctors to push for passage of the "COVID-19 and Pandemic Response Centers of Excellence Act," which would provide federal funding to chosen academic medical centers.
"If we're going to have future epidemics and be responding to them, people need to be trained in that experience," said Dr. Jay Varma, a professor at Weill Cornell Medicine.
"They should be distributed to community health centers. They should be distributed by mobile vans," Schumer said.
Health officials urge people to get vaccinated and get a booster, especially heading into the holidays.
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