The 46-year-old man was traveling from Minnesota to Massachusetts on a business trip in April 2014, with a connection in Chicago, according to a new report of the case. After he arrived in Massachusetts, the man developed a rash characteristic of measles, and his diagnosis was confirmed with a lab test.
As far as he knew, the man had not been around anyone with measles, and he hadn't traveled out of the United States.
But shortly before his case was reported, health officials in Minnesota had been investigating the case of a sick 19-month-old child, who had come down with measles while on a flight from India to the United States. The family with the sick child had changed planes in Chicago, and flown to Minneapolis.
Officials tracked down people who were on the child's flights, but no one on these planes appeared to have become sick.
Once officials heard of the man's case, they figured out that both the man and the sick child had traveled through the same gate in Chicago. The man had exited his plane in Chicago, using the same gate where the family with the sick child was waiting to board. [The 9 Deadliest Viruses on Earth]
"Although transmission could have occurred anywhere in the airport where the child and the adult shared airspace, it most likely occurred in the gate area during the 46-minute interval between the arrival of the adult's flight and the scheduled departure of the child's flight," the researchers, from the Minnesota Department of Health, wrote in the June 26 issue of the CDC journal Morbidity and Mortality Weekly Report.
"The child's family likely would have been preparing to board near the front of the gate area when the arriving adult exited his aircraft and passed through the area," the researchers said.
A test determined that the man's measles virus was genetically identical to that of the child. Both the man and the child recovered from their illness without complications.
Measles is a highly contagious disease that can be spread through the air. "The infectiousness of measles is evident when considering that transmission in this case occurred at a domestic terminal during a short period with brief contact," the researchers said.
The man didn't know whether he had been vaccinated against measles. The child had received one dose of the measles vaccine, but the single dose appears to have failed to protect the child. The case also underscores the CDC's recommendation that children older than age 1 receive two doses of the measles vaccine before they travel.