A horrible year for measles is about to get worse, according to a Northwestern University pediatric infectious disease specialist. Why it matters: The U.S. is already facing its most measles cases in 33 years,

Thanks to the introduction of a vaccine in 1963, measles was declared eliminated in the US in 2000. Now the highly contagious disease has reemerged as a threat as declining vaccination rates fuel outbreaks around the country.