Two cases of a coronavirus variant that originated in the United Kingdom and believed to be significantly more contagious have been identified in New York City.
Mayor Bill de Blasio announced the news Wednesday morning during a press conference at City Hall. It is the first time that health officials have discovered the variant, known officially as B.1.1.7., in New York City.
Dr. Dave Chokshi, the city's health commissioner, said that one of the cases involved a Manhattan resident, while the other involved someone from Queens. Both were originally diagnosed in late December, he said. Their samples then underwent genetic sequencing.
Health officials learned the results of that process early Wednesday, he said.
The cases were said to be handled through the city's test and trace program. Chokshi did not provide further details, including whether the two individuals had recently traveled to the U.K.
Altogether, health officials have found 15 cases of the variant statewide, with the first being a jewelry store worker in Saratoga Springs who had no travel history. At least 10 U.S. states and 50 countries are known to have cases of the variant.
U.S. health experts are increasingly worried about the possibility that community spread is now driving the cases. Some preliminary findings suggest that, while the variant does not cause more severe illness, it is 50% more transmissible, on average, than the original strain, according to researchers at Imperial College London. In the U.K., which has better surveillance of viral mutations, the variant has spurred shutdowns and tighter restrictions.
On Wednesday, federal authorities announced that all international passengers coming to the United States will first need to show proof of a negative coronavirus test, a move that reduces but does not entirely eliminate the risk of the virus spreading to the country.
Mayor de Blasio has called on the federal government to go further by banning all travelers from Britain.
"We need those flights canceled," he said Wednesday.
He said that older New Yorkers and those with pre-existing health conditions should now be especially cautious.
"Don't take chances," de Blasio said.
Dr. Jay Varma, the mayor's top health advisor, said the variant was a "very urgent and real concern" for the city. He said there was also a "theoretical concern" that people who have compromised immune systems may be more likely to have mutations of the virus.
City health officials said people should redouble their efforts to protect themselves from the virus, including mask wearing, social distancing and getting tested.
Other health experts said they were not surprised by news of the variant being found in New York City, which continues to see untold numbers of domestic and international travelers.
Dr. Denis Nash, an epidemiologist at CUNY, said his first thought was that the new evidence of the variant underscores the importance of accelerating vaccine rollout, so as to limit the potential spread of virus, including the new variant.
Similarly, Dr. Jeffrey Shaman, a Columbia University professor of environmental health sciences, said that the news should encourage the city to ramp up its vaccination among those 65 and older, particular those with pre-existing conditions.
"This is the most important target group if we are to prevent hospitalizations and death," he said.
This story has been updated with the latest number of variant cases in New York announced by the governor's office.