(WBBM NEWSRADIO) -- The Illinois Department of Public Health says there's a "very concerning trend" here in Illinois and nationally with measles cases.
New York City has declared a public health emergency, with more than 280 cases of measles confirmed there since October.
The state of Illinois confirms seven measles cases so far this year. That is small by comparison to New York City, but higher than normal for this point in the year over last year.
"The number of cases nationally at this point in time is above what they were for all of 2018,” said Dr. Jennifer Layden, chief medical officer and state epidemiologist for the state health department.
"There's a very concerning trend where we are seeing more measles cases nationally as well as -- in this point in time -- Illinois."
Dr. Layden said more than 98 percent of school children (more than 2.1 million kids) in the state are vaccinated for the measles. She added there are pockets of communities where vaccine rates are lower, often because of religious exemptions.
Illinois statistics show that more than 17,600 students got religious exemptions from the measles vaccine requirement.
One Chicago private school, for example, had a 74 percent vaccination rate - with 62 religious exemptions.
"When the vaccine rate goes anywhere below 95 percent for that population - or whatever population or community you're talking about - there's a risk for significant spread,” Layden said.