Officials confirm the first case of the South Africa variant in a New York resident.

A person from a suburb east of New York City has been confirmed as the first New York resident to have been infected by a more contagious variant of the coronavirus that emerged in South Africa, Gov. Andrew M. Cuomo said on Sunday.

Few other details were offered about the case, including specifically when it was confirmed or whether the individual who was infected, a resident of Nassau County on Long Island, had recently traveled. It was not the first case of the South Africa variant to be found in New York; Mr. Cuomo announced last Monday that the variant had been detected in a man from Connecticut who was hospitalized in New York City.

The variant, known as B.1.351, was originally identified in South Africa in December, and has since been found in dozens of other countries and at least nine states, including California, Texas and Virginia. The variant carries mutations that help it latch on more tightly to human cells and that may help the virus evade some antibodies.

Its emergence in New York, which officials had warned was inevitable, underscored the dangers posed by new variants that may be more infectious or resistant to vaccines, particularly as the state’s vaccination effort continues to be hampered by a limited supply of doses.

“We are in a race right now — between our ability to vaccinate and these variants which are actively trying to proliferate — and we will only win that race if we stay smart and disciplined,” Mr. Cuomo said in a statement on Sunday.

Two weeks ago, South Africa halted the use of the AstraZeneca-Oxford vaccine after evidence emerged that it did not protect participants in a clinical trial from mild or moderate illness caused by the variant.

Scientists in South Africa have also said that the immunity acquired by people infected by earlier versions of the coronavirus did not appear to protect them from mild or moderate cases when reinfected by the South Africa variant.

The Food and Drug Administration is working on a plan to update vaccines if the variant surges in the United States.

But Mr. Cuomo on Sunday also offered reason for optimism, noting that the statewide rate of positive test results was less than 3 percent for the first time since November. He said that hospitalizations also continued to decline statewide.