About 800 students at St. Charles East High School were ill with norovirus-like symptoms, according to Jim Blaney, the director of school and community relations for St. Charles District 303.
The school district said it was working with the Illinois Department of Public Health to more clearly identify the virus and following norovirus procedures in the meantime.
"The CDC (Centers for Disease Control and and Prevention) recommends that people with norovirus be symptom free for 48 hours before returning to normal activities.
"With that in mind, classes at St. Charles East High School are canceled on Wednesday, January 11, and will resume on Thursday, January 12," it said in a statement Tuesday.
Parents have been asked to keep students at home and "not allow groups of students to congregate."
In a news conference Monday
, Blaney said the school became aware of a potential outbreak on Saturday when 10 of the 14 members of the school's basketball team were unable to play due to illness. Athletes in other sports also became ill.
The school's principal emailed parents advising them of the situation and asking whether their children were also sick and if so what their symptoms were.
It became apparent that a number had the symptoms of a stomach virus, Blaney said.
The school was open on Monday, but as of 10 a.m. 800 of its 2,500 students were absent, he said. Tuesday's classes were canceled.
Blaney said it could not definitively be confimed that the ill students had norovirus.
But he said St. Charles East High School and other schools in the district had started using a different, bleach-based cleaning solution in response.
"The normal solution is pretty good at taking care of everything -- it's not that effective against norovirus."
He said the school district was doing what it could to provide a safe and clean environment and that parents should keep sick students at home.
"You have a lot of kids in a confined space and they share phones and they share drinking bottles and they do things that you know -- are not exactly the greatest hygiene."
Norovirus causes around 20 million cases of gastrointestinal illness in the United States each year, according to the CDC
, and it spreads easily in any area of close contact.
The virus causes inflammation in the stomach and intestines, leading to stomach pain, nausea and diarrhea. These symptoms typically last one to three days. Other symptoms include a fever, headache and body aches, according to the CDC.