The Philadelphia Department of Public Health announced the city's first case of Zika virus on Monday.
The infection was identified in a 60-year-old woman who recently returned from a trip to the Caribbean.
She was not hospitalized, officials said, and is recovering without complications.
The Zika virus is most commonly transmitted from the bite of a mosquito, and many people infected do not get sick. Medical authorities say most people recover in about a week from symptoms such as fever, rash and joint pain.
But health officials are investigating whether there is a link between Zika infections in pregnant women and a rare birth defect called microcephaly, in which babies are born with abnormally small heads
If you travel to areas where the Zika virus is widespread, you are reminded to take measures to avoid being bitten by mosquitoes:
-Wear long-sleeved shirts and long pants when going outside.
-Stay in places with air conditioning or that use window and door screens to keep mosquitoes outside.
-Sleep under a mosquito bed net if you are outside and are not able to protect
-Use an EPA-registered insect repellent, in accord with the manufacturer's directions.
Philadelphia residents with questions about Zika virus can call the Philadelphia Department of Public Health's Division of Disease Control at 215-685-6740.
The World Health Organization has declared it a global emergency.