Of the school's 637 students, 88 are suffering from flu-like symptoms.
All students have to leave campus by 5 p.m. Tuesday. Campus activities are cancelled until Monday. Dorms are expected to re-open Sunday afternoon.
"My understanding in the 30 year history of IMSA we haven't had to close for the flu before," said Tami Armstrong, director for public affairs at IMSA.
Based on information from both Kane County Health Department and Rush Copley Medical Center, the school decided to close to lessen the risk of getting more students and staff sick.
"This is one of the most severe seasons in a long time. Probably the most since H1N1 in 2009-2010," said Tom Schlueter, of the Kane County Health Department.
Tuesday morning, students who live downstate boarded a coach bus to get home. In the meantime, the buildings will be cleaned and disinfected.
"Our facilities team will be diligently following the CDC guidelines and that includes peroxide based solution on all hard surfaces, hospital grade sanitation for bathrooms and floor surfaces," Armstrong said.
Sophomore Brandon said he worried about making up for lost time, but agrees with the school's decision to send students home.
"I think it was really smart that IMSA sent us home so that not everyone else got sick," said Young-Eleazar.