Intermittent occurrence of health care-onset influenza cases in a tertiary care facility during the 2017-2018 flu season.

Health care-onset influenza (HOI) poses a major risk for hospitalized patients. During the 2017-2018 season, 37 HOI cases out of 382 inpatients (9.7%) with influenza were detected in a tertiary care hospital. HOI and community-onset influenza cases peaked simultaneously, and employee absenteeism was delayed by 1 month. A HOI to community-onset influenza case-comparison revealed associations with placement in rehabilitation, leukocytosis, health care-associated infections, and elevated mortality rates. Interventions should be selected based on the epidemiology of influenza occurrence.