SPOKANE, Wash. -

It's not the kind of record you want to break. The Centers for Disease Control and Prevention say we've reached a 20-year high for measles cases in the United States.


The U.S. has seen 288 cases of measles this year with outbreaks in 18 states. 15 cases have been reported in Washington since January.


Most people infected have not been vaccinated against measles. It's an illness that was once so rare, some doctor have never seen the symptoms, making measles somewhat difficult to diagnose in the early stages. 


To put this latest outbreak in perspective, consider that in 2004, there were only 37 cases of measles nationwide for the entire year. The United States has already recorded nearly 300 and it's only May.  


Some parents say it's their choice not to vaccinate their children, but the CDC warns the disease spreads most quickly in areas with large populations of unvaccinated people. That can be dangerous to young children and the medically fragile.


"Your children need to be vaccinated on time and fully," said ABC News Chief Medical Editor Richard Besser. "I met a baby yesterday, 8 months old, got measles because people around him were not vaccinated. The other [thing] is, if you're traveling overseas, you need to make sure you've had two doses of measles vaccine so you don't get infected and bring it back."


That's because in some parts of the world, measles are still prevalent. Cases in Ohio spread quickly because someone traveled to the Phillipines and came back infected, spreading the disease to members of the unvaccinated Amish community.


For more information about the disease and how it's spreading, click here or go to my Facebook page.