Maintaining Measles Elimination — Achievements and Challenges

Endemic measles transmission was declared eliminated in the United States in 2000, but importations of measles virus continue to occur. In 2011, the highest number of measles cases was reported since 1996. The vast majority of cases were unvaccinated or had unknown vaccination status. Age-specific incidence was highest among infants age 6-11 months, followed by those age 12-15 months and 16 months-4 years. In 2011, the number of measles importations was the most reported in over a decade; most importations were among unvaccinated US residents who traveled abroad. About half of all cases reported in 2011 were associated with outbreaks (defined as 3 or more associated cases). The increased incidence of measles in 2011 is related to increases in measles in countries more frequently visited by US travelers although the risk of importation is a global problem. The measles epidemiology highlights the importance of vaccination, particularly prior to international travel as well as timely public health interventions to reduce transmission and highlights the challenges for maintaining measles elimination. Heightened awareness of these issues is critical to the maintenance of measles elimination in the US.