It’s pretty much a given at this point that no one enjoys air travel. The indignity of the security line. The battle for an overhead bin. The anxiety of recognizing you’re in a middle seat, and the agony of wondering whether that wailing toddler headed down the aisle is going to end up next to you.
To that long list of stressors, add another: You might catch measles. And you don’t even have to enter the tight quarters of an airplane cabin to be vulnerable. For the second time in two years, the Centers for Disease Control and Prevention has confirmed that someone caught the measles by walking past an infected person in an airport.
Last week, in its bulletin the Morbidity and Mortality Weekly Report (really, it’s called that; great title, no?), the CDC said that a toddler traveling from India gave a Minneapolis man the disease when the two passed each other in a Chicago airport gate in April. The man was getting off a flight; the toddler and family were waiting to board the same aircraft after it was emptied and cleaned. There was no direct contact between the two, but there didn’t have to be: virus-laden droplets of moisture breathed out by a measles victim can hang in the air for up to two hours, long after the infected person has gone somewhere else.
The child who had been in India (the CDC isn’t explicit—probably to avoid identifying the family—whether the child was from the country or just visiting) had had only one of the two recommended doses of measles vaccine, and broke out in the characteristic rash, plus a fever, during the long India-Chicago leg of the family’s trip. With the help of the airlines and several state health departments, the CDC tracked down all the other passengers on both flights, and found no other cases. Everyone was fully vaccinated, and thus protected against the disease.
Except the man at the gate. He apparently was not vaccinated, and he developed a rash and fever two weeks later while on a business trip to Massachusetts. The health department there put him into hospital isolation, and helped the CDC confirm that the molecular signature of the virus from both the man and the child were identical. In that brief moment of walking through the gate, the toddler had infected him.
It seems like a random coincidence—but this isn’t the first time it has happened. In January 2014, four people were infected with measles by passing through an airport gate in California. In that case, the cluster’s “patient zero” was never found. But the timing of the cases, plus molecular analysis, confirmed that all four of the known victims were infected at the same time, and did not pass the disease to each other. In that case, the virus came from the Philippines, and just as in the new episode, the people who caught the disease in California went on to carry it to other states: this time, New York, Wisconsin and Texas.
There are several things in these episodes worth unpacking. The first is how very contagious measles is; we tend to think of disease transmission as something that requires close proximity or bodily contact, but not being on the other side of a room. The second is how quickly a disease can be transported cross-country, and how rapidly chains of transmission get very complicated. From the CDC’s analysis of the 2014 episode:
…all four patients were linked to the same terminal gate during a 4-hour period on January 17, 2014. Patient 1, an unvaccinated man aged 21 years with rash onset February 1, traveled on two domestic flights on January 17 and 18 that connected at the international airport. Patient 2, an unvaccinated man aged 49 years with rash onset February 1, traveled from the airport on January 17. Patient 3, an unvaccinated man aged 19 years with rash onset January 30, traveled domestically with at least a 4-hour layover at the airport on January 17. Patient 4, an unvaccinated man aged 63 years with rash onset February 5, traveled on a flight to the airport on January 17.
Patients 1 and 2 traveled on the same flight from the airport and were seated one row apart; both spent time at the departure gate before the flight. Patient 3, whose flight departed after the flight of patients 1 and 2, also reported spending time at this gate area during the time that patients 1 and 2 were present. Patient 4 passed through the same domestic gate around the time the other three patients were waiting to depart.
The third is that we can be vulnerable to disease when we least expect it. Measles still flourishes in some developing countries, as well as in some parts of Europe; if you plan on international travel, you might expect that hazard. We mostly don’t think of random disease transmission as a risk within the US, but we should: The people in both these episodes were infected at domestic airport gates, not international ones. (The 111 adults and children infected with measles at Disneyland last year probably didn’t expect to run that risk either.)
And the final thing, of course, is that this is why we get vaccinated: not just to guard against the risks we can anticipate, but also to protect us against the ones we can’t. All the people infected in these accidental encounters either declined measles vaccination themselves, or had that decision made for them by family members. Because they forewent that safe, routine, long-established protection, they contracted a potentially perilous disease, and they put others—who were so far from the original case they had no idea of the danger—at risk.