The U.S. Centers for Disease Control and Prevention has urged Americans traveling or living abroad with their children to be sure the kids are vaccinated against measles, even those as young as 6 months.
Measles was declared eliminated in the United States in 2000. But cases are still turning up among Americans — especially unvaccinated children — returning from overseas travel.
The CDC said Thursday that 29 Americans came down with measles in the U.S. in January and February, seven of them young children. All had traveled abroad. Four children had to be hospitalized.
The disease is highly contagious. The virus is spread by coughing or sneezing, and remains viable in the air for up to two hours.
One traveler later diagnosed with measles passed through BWI-Thurgood Marshall Airport on Feb. 22, triggering a health alert for passengers present in the terminal's Concourse A that evening. No Maryland cases emerged from the incident, state health officials said.
"Measles importations and transmissions from imported cases continue to pose a threat to U.S. residents," the CDC said Thursday in its Morbidity and Mortality Weekly Report.
"Travelers can be exposed to measles in the country of travel or while en route to and from that country, in airports or on airplanes," the report's editors said. "These findings highlight the importance of reviewing the vaccination history of anyone planning international travel."
Once an expected hazard of childhood in the United States and elsewhere, endemic measles has been eliminated in the Americas through routine vaccinations. Maryland has not seen it since four cases were confirmed in 2009. All were imported.
But the measles virus continues to circulate in many other regions of the world, including some European countries where acceptance of vaccinations is low.
An estimated 30 million to 40 million cases still occur worldwide each year, with more than 730,000 deaths. It is the fifth most common cause of death worldwide among children younger than 5 years, said Dr. Lucy E. Wilson, a medical epidemiologist at the Maryland Department of Health and Mental Hygiene.
Measles typically produces high fever, runny nose, cough, and red and watery eyes, followed by a body rash. Severe cases can lead to pneumonia or encephalitis. One or two cases in a thousand are fatal, Wilson said.
"It can be contagious for four days before the rash appears," she said. Travelers can be exposed without realizing it. "And it is highly contagious. There are many cases in the literature of patients contracting the illness in an airport terminal or a hotel."
Pregnant women who are exposed may miscarry. Young children and people with compromised immune systems who have not been vaccinated are at particular risk from the virus.
"It's important for parents who are traveling outside the country and who have children either below the age of vaccination [1 year] or who have not completed their vaccinations to discuss with their pediatrician whether the child is eligible to complete the vaccinations or to get vaccinated at an earlier age," Wilson said.
People born in the U.S. before 1957, and those who have had measles or been vaccinated against it, are considered immune, the CDC said.
An estimated 90 percent of U.S. children ages 19 to 35 months have received the measles vaccine, usually as part of the childhood measles, mumps, rubella (MMR) vaccine, according to the CDC. Medical authorities now recommend vaccination of children as young as 6 months if they are traveling or living abroad.
The CDC study published this week found that 13 of the 29 measles cases reported in the U.S. in January and February were imported. The rest of the patients were exposed to people who were infected during overseas travel.
Of the seven children who got sick, five had traveled in India, Qatar, the Philippines and Nigeria. One was exposed to an infected European tourist in the Dominican Republic. The last had traveled to Haiti but is not believed to have been exposed there.
Of the seven U.S. children, ages 6 to 23 months, who came down with measles in January or February after traveling abroad, the CDC said four were hospitalized — two for diarrhea and dehydration, one for persistent fever and one for pneumonia.
All recovered. But in some cases their doctors failed to consider a measles diagnosis for days.
"Clinicians … should maintain a high level of suspicion for measles in patients with febrile rash illnesses and recent travel outside the United States," the CDC editors said.