The Centers for Disease Control and Prevention (CDC) is strongly advising Americans who are not vaccinated against measles to cancel any upcoming flights. This urgent warning follows new evidence that measles—a highly contagious virus—is spreading on U.S. airplanes.
The CDC has raised its travel advisory from recommending unvaccinated travelers to “consider alternative plans” to now urging them to “consider postponing their trips.” This change reflects growing concern over recent outbreaks linked to air travel.
Experts estimate that about 10 percent of U.S. adults—around 25 million people—may lack immunity to measles. This could be because they never received the measles, mumps, and rubella (MMR) vaccine or because their immunity has weakened over time.
Measles cases have recently appeared at the nation’s busiest airports amid a resurgence driven by low vaccination rates. The CDC has investigated dozens of passengers who were contagious during flights and confirmed at least one case where measles spread onboard.
All travelers are now urged to be fully vaccinated against measles before taking any international flights. In addition, doctors are advised to offer extra measles vaccines to domestic travelers heading to Texas, where over 700 infections have been reported this year.
The CDC’s latest update states that travelers can contract measles in many places, including airports, train stations, airplanes, tourist spots, and crowded events. Since early 2025, the agency has recorded 62 cases of travelers infected with measles during or shortly after flying in or within the U.S.
An investigation of 50 of these cases found evidence that measles spread during air travel in at least one situation. This is usually confirmed when infectious passengers were seated near each other.
The warning came after three passengers on the same Turkish Airlines flight to Denver tested positive for measles, including one vaccinated adult.
Although exact current data on U.S. adults without measles immunity is limited, historical figures suggest roughly 10 percent may be unprotected. With a U.S. adult population of about 258 million, this means around 25 million adults could be vulnerable.
Most confirmed cases—about 90 percent—stem from outbreaks within the U.S., not from travel abroad.
Measles symptoms typically appear seven to 21 days after exposure. They include a blotchy rash, fever, cough, and runny nose. The virus spreads through airborne droplets from coughs and sneezes and can linger in the air for up to two hours.
Measles is especially dangerous for young children. The CDC reports that one in 20 unvaccinated children with measles develop pneumonia, and one in 1,000 suffer fatal brain swelling.
So far in 2025, 1,088 Americans have been infected, and two unvaccinated young girls have died from the disease.
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