The second Texas health care worker with Ebola flew from Cleveland to Dallas on Frontier Airlines the day before presenting symptoms, the US Centers for Disease Control has said.
The CDC is asking the passengers to call the health agency so they can be monitored.
Infected Ebola patients are not considered contagious until they have symptoms.
As it reaches seven months since the Ebola outbreak started we take a look at the timeline of events leading up to the spread of the virus.
More than 100 British personnel are arriving in Sierra Leone to combat the Ebola outbreak in West Africa. Here's what else the UK is doing.
A man has been filmed helping an Ebola patient onto a plane without wearing any protective equipment.