By Sept. 30, 1918, with 260 cases in Chicago, Health Commissioner Dr. John Dill Robertson ordered isolation of known influenza cases at Cook County Hospital.

The large and sudden jump in new cases led Health Commissioner Robertson to order the immediate isolation at Cook County Hospital of all known cases. Realizing that hospital isolation would soon become impossible, he told residents to prepare to isolate themselves should they become sick.

Despite his hesitation, Health Commissioner Robertson did ask Chief of Police John Alcock to have his officers stop all persistent sneezers and coughers who did not cover their faces with handkerchiefs.