Measles May Occur in International Travelers
The April 8th MMWR Report from the U.S. Centers for Disease Control and Prevention notes measles was declared eliminated in the United States in 2000, but cases continue to occur among U.S. residents who have traveled to other countries, as well as among foreign visitors to the United States.
Measles was declared eliminated and has been maintained through high MMR vaccination coverage. MMR vaccine is recommended by the American Academy of Pediatrics for routine use in all U.S. children at age 12--15 months, with a booster at age 4--6 years.
Traveling changes the recommendations as measles remains endemic in much of the world. In accordance with the Advisory Committee for Immunization Practices (ACIP) recommendations, U.S. children who travel or live abroad should be vaccinated at an earlier age than those living in the United States because of the greater risk for exposure to measles outside the United States, and particularly outside the Americas.
Children aged ≥12 months who are traveling internationally should receive 2 doses of MMR vaccine, separated by at least 28 days. Children aged 6--11 months should receive 1 dose of MMR vaccine. Infants vaccinated before age 12 months should be revaccinated on or after the first birthday with 1 dose of MMR vaccine followed by a second dose at least 28 days later.
In the first 2 months of 2011, CDC received reports of seven imported measles cases among returning U.S. travelers aged 6--23 months; four required hospitalization. It is the young children who are at greatest risk for severe measles, death, or sequelae such as subacute sclerosing panencephalitis.
None of the seven children had received measles, mumps, and rubella (MMR) vaccine prior to travel outside of the United States.
The CDC reports in the first two months of this year 13 cases of "imported measles" among U.S. residents, including seven cases of measles among American infants aged 6 to 23 months who had traveled to other countries.
During 2001--2010, a total of 159 imported cases were reported in U.S. residents, including 47 (range: 3--8 per year) in children aged 6--23 months (three of whom had been vaccinated before travel).
Measles cases are classified epidemiologically according to the source of infection. An internationally imported measles case is defined as one resulting from exposure to measles virus outside the United States as evidenced by at least some of the exposure period (7--21 days before rash onset) occurring outside the United States and rash occurring within 21 days of entering the United States, with no known exposure to measles in the United States during that time.
All other U.S. cases are considered U.S.-acquired. Laboratory confirmation of measles is made by detection in serum of measles-specific immunoglobulin M antibodies, isolation of measles virus, or detection of measles virus by nucleic acid amplification in an appropriate clinical specimen.
The World Health Organization has more about measles.
Centers for Disease Control and Prevention; MMWR, April 8, 2011