The eight individuals were either confirmed to be infected, believed to have a high probability of having measles, or at high risk due to not being immune to the highly contagious virus and suspected of being in close contact with someone who has measles, CDC spokeswoman Caitlin Shockey told CNN.
She characterized the conversations as “pre-discussions” and said that state and local health departments contacted the CDC to say “we have people that we may have to place on the do not board list.”
The “do not board” list is a tool the federal government can use to prevent an infectious person from flying while sick, Dr. Martin Cetron, director of the CDC’s Division of Global Migration and Quarantine explained.
This measure has been used since 2007 for patients who have tuberculosis, and in 2014 was used twice for measles.
After trying to dissuade a passenger who is sick and contagious from traveling on a plane, state or local health officials may contact the CDC to request assistance. The agency then has to verify that attempts were made to prevent the individual from traveling and that the person has flight reservations. The CDC then speaks to the airline to arrange for any fees related to canceling the trip to be waved.
Then the CDC works with the Department of Homeland Security to place the person on a public health do not board list, which tells the airline not to issue a boarding pass, Cetron explained in an interview with CNN. Cetron said that it’s a persuasive option. “Ninety-something percent of the time when we inform people we want them to change their mind and we can tell the airline not to issue a boarding pass, they change their mind.”
In the instances that have come up this year due to measles, all of the individuals voluntarily decided not to travel without the CDC contacting them, Shockey said.
“The NYC Health Department has worked with two individuals who were not immune to measles to prevent them from flying during the 21 days after they were exposed to measles virus, while they were at risk for getting sick,” Patrick Gallahue, spokesman for the New York City Department of Mental Health and Hygiene said in an email. “No one has been placed on the ‘Do Not Board’ list during this outbreak, and we have worked with passengers to minimize the inconvenience of travel disruptions in order to protect the health of New Yorkers and other travelers. People have been very cooperative.”
Cetron also said that there has been a significant increase in the number of investigations due to passengers flying with measles, for example after someone has returned home from a trip and then is diagnosed with the virus but was contagious while they traveled. The CDC works with the airline to inform at-risk passengers of the possible exposure. A person with measles is contagious for four days before developing the tell-tale symptom of a rash four days after.
Of the 62 measles investigations on flights this year, “21 were from domestic flights, 14 inbound international, 5 outbound IHR (outbound flights from the US to another country reported to CDC by a foreign agency) and 22 international IHRs (international to international flights with a US resident reported to CDC from a foreign agency),” Shockey said, adding that “the difference on the last two is that Outbound IHRs are from a US airport to a Foreign Airport. International IHRs are flights from an international airport to another international airport with a US resident on board.”
“The problem is most of the time when we do contact investigations the time window for measles is narrow … we are hearing about it after the fact so [our] ability to know about cases before they travel is infrequent,” Cetron said.
There was one known secondary case of measles this year, meaning a passenger became infected while traveling from another infected traveler, Cetron told CNN. “We can’t always say it was the cabin environment for sure.”
Cetron said the best way to for anyone to protect themselves and others from measles while traveling or any time is to get an MMR vaccine.