At least seven children have been born with birth defects and five pregnancy losses related to Zika in the United States. The lifetime cost of care is estimated to be $10 million for each sick child.

“Each case is a tragedy,” Dr. Frieden said. “A child that may never walk or live independently.”

The New York case is the first in which a man was infected by a woman, and it raises the prospect that other men — with no travel history to Zika-affected areas and no reason to suspect that they might have the virus — could become infected and pass the virus on, creating a new chain of transmission.

In the report, researchers found that a man, who was in his 20s and did not travel outside the United States during the year before his illness, contracted the virus after one instance of vaginal intercourse, without a condom, with a woman who had recently returned from a country where the virus is endemic.

Dr. Mary T. Bassett, the city’s health commissioner, said there were several factors in this case that might have raised the risk of infection: The man was uncircumcised, the woman was in the early stages of her illness when her viral load was high, and she was also at the beginning of her menstrual cycle.

The woman, described as being in her 20s and not pregnant, had sex with her partner the day she returned to the city. The report does not name the country she visited, but the virus is now widespread in nearly 50 countries throughout South America and the Caribbean.

“She reported having headache and abdominal cramping while in the airport before returning to N.Y.C.,” the report said. The next day she developed a number of symptoms associated with Zika, including fever, fatigue, a rash, back pain, swelling of the extremities, and numbness and tingling in her hands and feet.