A patient infected in Dallas, Texas, is likely to have been infected by sexual contact, the Centers for Disease Control (CDC) told the BBC.
The person had not traveled to infected areas but their partner had returned from Venezuela.
Zika is carried by mosquitoes and has been linked to thousands of babies being born with underdeveloped brains. It is spreading through the Americas and the World Health Organization (WHO) has declared the disease linked to the virus a global public health emergency.
