There is a confirmed case in city of Barrington and another probable case in Lake Zurich.
In a newsletter, school officials assured parents that they shouldn't feel overly concerned about the case.
What was previously considered a "cluster" is now a confirmed outbreak of the highly contagious mumps disease at suburban Barrington High School, Lake County Health Department officials announced Tuesday.
But county health officials continue to field reports of probable and suspected cases since first reporting a confirmed mumps case in Barrington High School on February 28. An Arlington Heights middle school reported a possible case, but the student's test results came back negative for the mumps Tuesday.
Mumps is spread through saliva and respiratory secretions often related to coughing, sneezing, or touching.
Officials from Chicago Public Schools alerted parents Monday of a possible case of mumps at a North Side elementary school, the Chicago Sun-Times reports.
"We've done some thorough cleaning of our facilities, especially over the weekend when no one was in the building, we were cleaning with a bleach based solution and focusing on the high touch areas like door knobs, bathrooms tables and chairs", said Morgan Delack of Barrington School District 220.
District 220 officials initially notified parents, students and staff of the first confirmed case of mumps in a districtwide message February 28, describing how a student contracted the viral disease.
"If you are not feeling well, stay home", McWilliams said to students and faculty.