By Jeremy Ross

CHICAGO (CBS)– City officials have announced the first confirmed measles case in Chicago this year. Now, officials are looking for people who may have been exposed.

At least one visitor carried the highly infectious disease with them throughout visits to popular places in the city.

In a video chat interview, Dr. Julie Morita, Commissioner for the Chicago Department of Public Health, she told CBS 2 about the first measles case her agency has identified this year.

The exposure may have occurred on the train on May 16 or by bus around the loop, in stores on State Street between Monroe and Randolph and on South Canal Street.

Other exposed areas may include around Millennium Park and on the campus of the University of Illinois at Chicago, specifically UIC’s student center east.

The Blue Line to and from and including the nation’s busiest airport is also a possible exposure point.

“The person did travel through O’Hare airport and were working closely with O’Hare,” Morita said.

The Centers for Disease Control and Prevention said so far this year, 839 cases of measles have been confirmed in 23 states. All of last year that number was 372. That’s the greatest number of cases reported in the U.S. since 1994 and since measles was declared eliminated in 2000.

But, Morita said Chicagoans are better prepared than other communities for this disease.

“Our vaccine coverage levels are so high, 94% or more of children actually have immunity,” Morita said. “This is just a good reminder to people to get vaccinated.”

Health officials say do not panic, but do have a conversation with your doctor if you’re not sure you have immunity to measles.

“If you were in O’Hare or using public transit or shopping in certain areas in the City of Chicago, check your immunization record,” Morita said.