In recent years, the number of measles cases in the United States has increased, According to the CDC, this is due to unvaccinated travelers contracting measles overseas and then spreading the virus when they return to the US.<ref>[http://www.npr.org/blogs/health/2011/05/24/136618682/u-s-measles-cases-hit-15-year-high?ps=sh_sthdl]</ref> | In recent years, the number of measles cases in the United States has increased, According to the CDC, this is due to unvaccinated travelers contracting measles overseas and then spreading the virus when they return to the US.<ref>[http://www.npr.org/blogs/health/2011/05/24/136618682/u-s-measles-cases-hit-15-year-high?ps=sh_sthdl]</ref> |