Now Women Can Spread The Zika Virus To Men; A New York Case Confirms It

ST. CROIX — With a sharp increase of the Zika virus affecting the territory this week — the Department of Health reported 15 news cases late Tuesday — it has now been confirmed that women can spread the virus to men, the first case being documented in New York City.

The confirmation raises the prospect that the disease could spread more widely beyond the countries where it is already endemic and largely transmitted by mosquitoes, including neighboring island Puerto Rico. For months, there has been growing concern about the dangers of sexual transmission, but until now the virus has been thought to pass only from men to women or between two men.

“This represents the first reported occurrence of female-to-male sexual transmission of Zika virus,” said a report issued on Friday by the federal Centers for Disease Control and Prevention and the New York City Department of Health and Mental Hygiene.

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.

She reported that her period, which began that day, was also heavier than usual.

Her primary care physician sent blood and urine samples to the city and state health department laboratories for testing. The tests detected the virus but not antibodies to it, which suggested she was newly infected; it takes four or five days for the body to begin producing antibodies.

Seven days after intercourse, the woman’s partner developed a fever, followed by a rash, joint pain and conjunctivitis. The report said the man had not had any other recent sexual partners or been bitten by a mosquito within a week before his illness.

Three days later, the man went to the same primary care physician who had diagnosed Zika in his partner. The physician sent samples of his urine to the same laboratories, and the virus was detected.

According to the report, the man “did not report noticing any blood on his uncircumcised penis that could have been associated with vaginal bleeding or any open lesions on his genitals immediately following intercourse.”

Zika is spread primarily through the bite of an infected Aedes species mosquito. The most common symptoms of Zika are fever, rash, joint pain, and conjunctivitis (red eyes). The illness is usually mild with symptoms lasting for several days to a week after being bitten by an infected mosquito. People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. For this reason, many people might not realize they have been infected or may be infected and have no symptoms. Zika can also be spread sexually.

The World Health Organization and the C.D.C. have urged pregnant women against travel to more than 45 countries in which the Zika virus is spreading, mostly in the Caribbean and Latin America. All pregnant women who have been to these regions should be tested for the infection, health officials have said, and should refrain from unprotected sex with partners who have visited these regions.

The Zika virus has been linked to unusually small heads and brain damage in newborns — called microcephaly — in children born to infected mothers, as well as blindness, deafness, seizures and other congenital defects. In adults, the virus is linked to a form of temporary paralysis, called Guillain-Barré syndrome.

“The more we learn about Zika, the more concerned we are,” Dr. Thomas R. Frieden, the director of the C.D.C., said during a recent conference call with reporters.

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.

Sources: C.D.C., New York City Department of Health and Mental Hygiene, New York Times.