Testing was later restricted to patients at high risk for complications from influenza; although, this did not occur until the end of the study period. Laboratory confirmed cases of pHlNl were reported to local health units who performed detailed case investigations using a standardized case report form. Case information was entered into the integrated Public Health Information System (iPHIS), the information system used by Ontario's 36 public health units for reporting case information on reportable communicable diseases to the MOHLTC.