Thousands of passengers may be at risk after a woman who tested positive for measles traveled through airports in Washington, D.C., Denver and Albuquerque last Tuesday.
Measles is the highly contagious respiratory disease that's transmitted through the air.
The Centers for Disease Control and Prevention is trying to track down everyone who may be in danger from that exposure.
"Public health authorities considers this a medical urgency, if not an emergency. They will do everything they can to track down everyone to see if they are indeed protected," William Schaffner, chair of the Department of Preventive Medicine at Vanderbilt Medical School.
The 27-year-old woman flew from the United Kingdom to Dulles International Airport in Washington, D.C., and then to Denver, where she spent 3 hours before flying to Albuquerque, N.M. Passengers traveling on those planes or passing through those airports may have been exposed.
The measles takes 18 days to develop so the scope of exposure is still unknown. The Colorado Department of Public Health and Environment issued a warning yesterday advising people traveling through concourse C at the Denver International Airport to monitor themselves for any early symptoms - including fever, runny nose, cough - from March 1 to March 12.
The C.D.C. says the woman who tested positive was not immunized because of her religion.
"Measles is the most communicable virus that we know, and it can be transmitted," Said Schaffner. "Not just person to person, but over considerable distances because it wafts in the air and then people can inhale it when they are some distance away."
In the United Sates, about 60 cases of measles are reported to the C.D.C each year, and children who never received an immunization or adults who declined to be immunized are at greatest risk.
Public health officials are also working in Boston, as a third suspected case of measles is being reported. All of the patients had measles symptoms, according to the Boston Herald.
People are considered immune to measles if they were born in the United States before 1957, previously had measles, or were vaccinated against it.