CBS 2 has learned another 41 cases have turned up at the University of Chicago medical campus.
Loyola University Medical Center microbiologist Paul Schreckenberger says last week alone, 21 patients tested positive for influenza. All but one of those cases were the 2009 H1N1 swine flu.
Rush University Medical Center is taking the extra precaution as the virus surges in Illinois.
A University of Chicago researcher says the 2009 flu pandemic has provided clues that might help get rid of the disease entirely one day.