Epidemiology of measles--United States, 2001-2003.

Measles is a highly infectious, acute viral illness that can cause severe pneumonia, diarrhea, encephalitis, and death. To characterize the epidemiology of measles in the United States during 2001-2003, CDC analyzed data reported by state and local health departments. This report summarizes the results of that analysis, which indicated that no endemic measles virus is circulating in the United States; however, imported measles cases continue to occur and can result in limited indigenous transmission. Maintaining immunity through high vaccination coverage levels is essential to limit the spread of measles from imported cases and prevent measles from becoming endemic.