"Flu season hit early and it has hit hard," Dr. Bechara Choucair, commissioner of the Chicago Department of Public Health, said in a statement.
Throughout Tuesday, four to eight hospitals across Illinois were on bypass at any given point -- they could not handle any more non-critical patients and ambulances with non-emergency cases were directed to other hospitals, while Monday, 11 Chicago-area hospitals were on bypass status, the Chicago Tribune reported.
The University of Chicago Medical Center had to pair patients with similar infections and order more supplies such as surgical masks and testing materials, Dr. Emily Landon, an epidemiologist at the medical center said.
"We are seeing a ton of influenza cases," Landon told the Tribune. "Our hospital is incredibly busy."
Melaney Arnold, spokeswoman for the Illinois Department of Public Health, said for the first week of the year, 24 Illinois hospitals went on bypass for nearly 400 hours -- a fourfold increase in the amount of time that hospitals weren't accepting non-critical patients compared with the first week of 2012, when seven hospitals logged fewer than 100 hours of bypass time.
Dr. David Zich of Northwestern Memorial Hospital in Chicago estimated more than 35 patients with flu-like symptoms were in the emergency department's waiting room Monday night, but most did not require medical attention.
"The flu in and of itself is not a reason to come to the emergency department," Zich told the Tribune.
Influenza patients need not visit an ER unless he or she has difficulty breathing or has another serious illness, such as heart disease, Zich said.