(BARRINGTON) Lake County health officials have declared an outbreak of mumps in northwest suburban Barrington.

Three cases of the highly contagious disease were confirmed at Barrington High School, along a fourth unrelated case in the suburb, the Lake County Health Department announced Tuesday.

Seven additional cases are considered “probable” and 20 more were deemed “suspect” at two high schools, two middle schools and elsewhere in the surrounding area, health officials said.

Mumps is passed through saliva and mucus, especially by sharing cups or other items, officials said. Up to half of people who contract the virus at first show mild or no symptoms, which include fever, headache, loss of appetite and tender salivary glands under the ears.

“With spring break approaching, and other warm-weather social events coming up, students should be particularly cautious, especially if they are planning to travel,” said Mark Pfister, the health department’s executive director.