(Reuters) - New York is expanding free Zika virus testing to pregnant women who had unprotected sex with a partner who had traveled to a Zika-infected area, the state's health department said on Wednesday.
The state already offers testing to pregnant women who traveled during pregnancy to an area where Zika is circulating, and to non-pregnant women, men or children who developed symptoms of Zika within four weeks of travel to an area with active Zika transmission.
Only one in five people infected with the Zika virus will develop symptoms, which are typically mild, but there have been increased reports of a birth defect known as microcephaly, a condition defined by unusually small heads that can result in developmental problems.
Much remains unknown about Zika, including whether the virus actually causes microcephaly. Brazil said it has confirmed more than 640 cases of the disease and considers most to be related to Zika infection in mothers. The country is investigating more than 4,200 additional suspected cases of microcephaly.
The World Health Organization on Tuesday advised pregnant women not to travel to areas with active Zika virus and said sexual transmission is "relatively common."
WHO director-general Margaret Chan told reporters that microcephaly is only one of several birth abnormalities associated with Zika during pregnancy. Others include death, retardation and injury to the nervous system.
Dr. Howard Zucker, commissioner of New York's health department, said that the department is expanding testing "as evidence has emerged that the risk of sexual transmission is greater than previously known."
The department is investigating one possible case of sexual transmission. It recommends, along with the Centers for Disease Control and Prevention, that men who have traveled to or lived in an area with active virus transmission abstain from sex or use condoms throughout their partner's pregnancy.
The department is also working with local health officials in counties inhabited by a type of mosquito that could potentially carry the Zika virus to update and implement a mosquito surveillance and response plan.
In Central and South America the virus has been transmitted mainly by the Aedes aegypti species of mosquito, which is not present in New York State. But a related species, known as Aedes albopictus, is present in New York City and surrounding counties. Researchers are not sure if Aedes albopictus can effectively transmit the virus.
The WHO said on Wednesday that widespread spraying to eliminate mosquitoes had failed to stop the spread of dengue fever and the same may be true of Zika.
Reporting by Toni Clarke in Washington; editing by Grant McCool