CDC steps up measles travel warning after spread in airplane

The Centers for Disease Control and Prevention has updated its warning about the risk of contracting measles while traveling, after the agency tallied dozens of cases so far this year in travelers who were infectious while flying on airplanes within the U.S.

"Travelers can catch measles in many travel settings including travel hubs like airports and train stations, on public transportation like airplanes and trains, at tourist attractions, and at large, crowded events," the agency now says, in an update published Wednesday.

Since the beginning of the year, the CDC has received at least 62 reports of travelers who were contagious with the highly transmissible virus while flying into the U.S. or within the country, a spokesperson for the health agency told CBS News in a statement.

After investigating 50 of those travelers, the CDC was able to determine that measles spread during air travel in at least one of those situations, the spokesperson said. That is usually based on connecting confirmed cases of measles among airline passengers sitting near each other.

There have also been numerous public alerts in recent months about the possible risk of exposure in airports, after travelers were found to be contagious. "Exposures at the airport itself are more difficult to track, and state, local, and territorial health departments lead these investigations," the spokesperson said.

In its Wednesday update, the CDC dropped its list of countries now facing "high incidence" of measles. Instead, the agency now warns only that the virus is "an ongoing risk around the world, and more international travelers are getting infected."

In addition to this year's record surge of the virus within the U.S., health authorities in neighboring Mexico and Canada have also reported large outbreaks of measles.

The CDC also replaced a previous recommendation that Americans "consider making alternative travel plans" if they could not get vaccinated before departing, and now says travelers should "consider postponing their trip."

All travelers are recommended to be fully vaccinated for measles before going to any international destination. The CDC recently updated its guidance to doctors advising additional measles vaccines for some domestic travelers as well.

The changes come as the CDC's tally of measles cases has begun to show signs of accelerating again.

At least 1,088 cases of measles have been reported so far this year, the CDC said Friday, with two more states — Iowa and Nebraska — now reporting their first confirmed cases. Around 90% of confirmed cases are linked to outbreaks within the U.S., not travel outside the country.

A tally of cases backdated by when their symptoms began has climbed for a second straight week, in the agency's preliminary data, after falling from a peak in late March during the height of the outbreak in Texas and neighboring states.

While federal health officials have said that this Southwest outbreak now appears to be slowing, they have warned of the risk of renewed spread driven by travel.

"This outbreak does appear to be leveling off, but the affected states remain hypervigilant, and that's because it's travel season," the CDC's Dr. Manisha Patel, chief medical officer of the agency's National Center for Immunization and Respiratory Diseases, told a webinar published by the American Medical Association on May 15.

• Centers for Disease Control and Prevention
• Vaccine
• Measles