United Airlines will refund passengers with tickets to places affected by the Zika virus, or allow them to reschedule their trip at no cost, a spokesperson told Reuters. The Zika virus is a mosquito-borne illness linked to neurological birth disorder that has spread to at least 23 countries, including Mexico, Brazil, Haiti, Panama,Venezuela, and many more. Several cases have also been confirmed in Puerto Rico. The Centers for Disease Control and Prevention warned pregnant women not to travel to these destinations, as the disease is spreading rapidly, while public health officials in the affected areas are telling women not to get pregnant. Travelers took to social media Tuesday, wondering if ticket refunds were in the cards. American Airlines said it was refunding tickets to El Salvador, Honduras, Panama, and Guatemala, according to Reuters. Puerto Rico has 18 confirmed cases, according to a new report. The CDC issued travel warning for areas affected, including Puerto Rico, in January. This is a developing story.