Airlines are starting to offer refunds to passengers who have booked flights to countries in central and south America caught up in the Zika virus outbreak.
The relatively new mosquito-borne virus is connected with a neurological disorder that results in babies being born with abnormally small heads. There is no vaccine to prevent Zika or medicine to treat the infection.
British Airways said pregnant customers with flights to Sao Paulo and Rio de Janeiro in Brazil, or to Mexico City or Cancun (Mexico), could change their booking free of charge, delay their journey or choose an alternative destination. This applies through February.
American Airlines is offering pregnant passengers a full refund if they provide a doctor's note showing they are unable to fly to the following cities: San Salvador (El Salvador), San Pedro Sula and Tegucigalpa in Honduras, Panama City and Guatemala City.
United Airlines said its giving any customers "who are traveling to the affected regions the opportunity to rebook at a later date or receive a full refund."
The Zika virus has now spread to at least 25 countries. The Centers for Disease Control and Prevention is warning pregnant women against travel to those areas.
Health officials in several of those countries have told female citizens to avoid becoming pregnant, in some cases for up to two years.
All the airlines said they are constantly reviewing their policies on refunds and changes to bookings. United has linked to the Center for Disease Control's Zika travel advice, which now includes Central America, South America and the Caribbean.
A young girl from Los Angeles County who traveled to El Salvador was infected with the Zika virus, officials confirmed Tuesday.