Health officials in the US state of Texas say they have recorded the first case of the Zika virus transmitted by a local mosquito.
Up until now, all Zika cases in Texas have been contracted while travelling.
The virus, which started spreading rapidly through the Americas last year, has been linked to microcephaly, a rare birth defect.
Florida is the only other US state to have reported locally caught cases of Zika.
The Texas Department of State Health Services said the patient was a woman living in Cameron County, near the Mexican border. She is not pregnant, and has not recently travelled to Mexico or anywhere else with ongoing Zika virus transmission.
“We knew it was only a matter of time before we saw a Zika case spread by a mosquito in Texas,” said Dr John Hellerstedt, the heath department commissioner.
“We still don’t believe the virus will become widespread in Texas, but there could be more cases, so people need to protect themselves from mosquito bites.”
The state said it currently has no other suspected cases of local transmission.
The infection was confirmed by testing the woman’s urine. However, a blood test proved negative, meaning that the virus can no longer be spread from her by another mosquito.
The Zika virus often causes little or no symptoms, but experts believe it is linked to complications during pregancy, and could cause babies to be born with small heads and other developmental problems.
Texas has had 257 confirmed cases of the Zika virus, but all previous cases have been associated with travel.
When a Texan baby died from Zika-linked microcephaly in August, the health department released a statement making it clear that the mother had travelled to Latin America and said there were no additional local risks.
The health department said it was working with Cameron County and the Centers for Disease Control and Prevention to respond to the new, local case. It also confirmed a door-to-door awareness programme, starting immediately.