CHICAGO (WLS) -- Measles was thought to be eliminated 20-years ago in the United States, but it's still common in other parts of the world.
It's a serious, highly contagious disease caused by a virus, and is spread easily through the air when an infected person coughs or sneezes.
It can also be contracted by direct contact with infected nose or throat secretions.
Doctors in Illinois are doing what they can to urge people to get vaccinated.
Megan Glenn is keeping her son Remy busy while they wait for their appointment at Advocate Children's hospital in Park Ridge to get his measles vaccination.
"I feel that the risk for not vaccinating is much higher than any risk that there is for vaccination," she said.
For Glenn, there's no question that getting her son vaccinated is a necessary step in protecting him for life against the highly contagious disease.
"Just as we make them wear bicycle helmets and look both ways to cross the road before they go, we need to immunize them and protect them," said Glenn.
But health experts are battling an outbreak of measles that is now up to 465 cases nationwide so far this year. Seven of those cases are in Illinois.
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So doctors from different Health systems are ratcheting up the pressure on local families who opt out of vaccinations by sending letters to parents of children who are not vaccinated against the measles.
"It's really our job as trusted providers for the community to educate and dispel the myths to make sure people understand the science behind vaccination and how it's contributed to public health," said Dr. Frank Belmonte, Advocate Children's Hospital.
Doctors will go in their data bases to identify children who are not properly vaccinated and will send out hundreds of letters like this.
The hope is to protect families who live in pockets where many people in the community are not vaccinated in order to stunt the spread of the disease.
"Your first vaccination occurs at around 12 to 15 months and your second occurs at around 4 to 6 years of life so we look at those appropriate age windows and try to find who has the vaccination and who doesn't," said Dr. Mickey Caplan, North Shore Pediatrics.
As for Remy, it took just seconds to get vaccine that will give him lifelong protection.
More than 80 percent of the people infected by the measles in the U.S. are children.
Doctors say they will still care for kids who don't get vaccinations, but urge parents to immunize their kids.
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Measles outbreak: Illinois doctors redouble vaccination efforts as cases rise