Measles - United States, January 1-August 24, 2013.

Measles is a highly contagious, acute viral illness that can lead to complications and death. Although measles elimination (i.e., interruption of continuous transmission lasting ≥12 months) was declared in the United States in 2000, importation of measles cases continues to occur. During 2001-2012, the median annual number of measles cases reported in the United States was 60 (range: 37-220), including 26 imported cases (range: 18-80). The median annual number of outbreaks reported to CDC was four (range: 2-16). Since elimination, the highest numbers of U.S. cases were reported in 2008 (140 cases) and 2011 (220). To update measles data, CDC evaluated cases reported by 16 states during January 1-August 24, 2013. A total of 159 cases of measles were reported during this period. Most cases were in persons who were unvaccinated (131 [82%]) or had unknown vaccination status (15 [9%]). Forty-two importations were reported, and 21(50%) were importations from the World Health Organization (WHO) European Region. Eight outbreaks accounted for 77% of the cases reported in 2013, including the largest outbreak reported in the United States since 1996 (58 cases). These outbreaks demonstrate that unvaccinated persons place themselves and their communities at risk for measles and that high vaccination coverage is important to prevent the spread of measles after importation.