The first known case of a woman spreading the Zika virus to a man during sex has been reported in New York.
Until now, experts were only aware of the virus being spread by mosquito bites or men infecting their partners during sex.
The Centers for Disease Control and Prevention said: “The New York case involves a non-pregnant woman in her 20s.
“She had returned to New York city from travel to an area with ongoing Zika virus transmission.”
It did not specify where the woman may have been infected but the next day she developed fever, back pain, swelling and tingling in her hands and feet.
Doctors confirmed she had the virus, as did her partner, who had not travelled outside the US for the previous year.
Zika can cause birth defects, including the brain and skull deformity.