Last Updated Feb 4, 2016 9:00 AM EST
United Airlines is allowing pregnant flight attendants and pilots and any trying to become pregnant to swap out of flights to regions affected by the Zika virus, the carrier confirms to CBS News.
The story was first reported by the Reuters news agency, which says Delta Airlines has been letting crew members do the same since mid-January and a "small number" of crew members have.
Delta confirmed to CBS News that they are also accommodating crew members.
"This wasn't really a change of policy for us as we always are monitoring external factors and stand ready to work with any crew member who may have a health concern in the due course of their duties," said Delta spokesman Morgan Durrant. "But since Jan. 17 we've offered the option for any crew member (pilot and flight attendant) with concerns to swap out a scheduled trip if traveling to areas flagged by the CDC since Jan 17."
Routes to Latin America and the Caribbean are the ones that are impacted, the airlines told Reuters.
Zika, which is transmitted mainly by mosquitoes, has been linked to birth defects in Brazil -- particularly one in which babies are born with small heads.
"We have immediate concern about our members' health," Reuters quotes Sara Nelson, international president of the Association of Flight Attendants-CWA, as saying about United's policy.
"This issue is changing at a fairly rapid pace, (and) it's important that those updates are ongoing," she told Reuters, adding that airlines seem to be reacting more quickly to employee concerns than during past outbreaks, such as that of Ebola in 2014.
Carriers and hotel chains say they don't know yet whether Zika is affecting business.
However, says Reuters, "Top U.S. carriers, including United and Delta, are offering refunds for flights to impacted areas. Travel agents also say 'babymooners' - parents-to-be taking last-hurrah vacations - have backed out of trips and changed itineraries."
Concern about Zika risen due to a reported case of sexual transmission in Texas and the World Health Organization declaring a global health emergency due to Zika.
The U.S. Centers for Disease Control and Prevention is urging pregnant women to mull putting off trips to areas hit by Zika.
There is no treatment or vaccine to combat it.