Background: Nosocomial influenza infections can be caused by direct patient-to-patient transmission, as well as bidirectionally between patient and healthcare workers (HCWs). Lapses in infection control practices (droplet precautions), and HCWs who come to work despite influenza-like illness (ILI, ie, “presenteeism”) can potentiate transmission. Cocirculation of >1 strain of influenza may complicate efforts to track infections. We describe a multidisciplinary response that helped control a late winter nosocomial influenza outbreak at a time when both influenza A/H3 and A/H1(2009) were prevalent in the community. Methods: Infection control practitioners detected a potential cluster of influenza A/H3 cases on an adult general medicine unit during the middle of March. The patients were spread out in nonadjacent rooms in a 30-bed unit, which suggested a possible common shared source. Further investigation revealed other potential clusters. Hospital incident command (HIC) was deployed to assess and respond to the outbreak; the incident commander was the chief medical officer (CMO) and the hospital epidemiologist was the subject matter expert. Other HIC roles were manned by nursing leadership, hospital administration, employee health, and the clinical laboratory. The group met at least daily (teleconference on weekends) until the extent of the outbreak was known and no new cases were identified. Results: A multipronged approach was used to control the outbreak. HCWs who reported to work with ILI symptoms were referred to employee health, tested with a PCR-based influenza screening panel, and sent home. Inpatients with ILI symptoms were tested with a comprehensive respiratory virus panel that could distinguish influenza A/H1(2009) from A/H3. Inpatients who were newly positive for influenza were evaluated to determine whether they were epidemiologically linked to an existing cluster, represented a new case of nosocomial acquisition, or were presumed to be community-acquired. The outbreak involved separate clusters caused by A/H3 and A/H1(2009) that affected 40 patients on 9 clinical units. Conclusions: A key component of the response was implementation of a local “mask rule”: all physicians, nurses, other employees, students, and visitors were required to wear surgical masks on affected floors regardless of their vaccination status. In addition, the hospital IT team developed a dynamic spreadsheet that listed information about all nosocomial cases (location, date of onset, etc), as well as ILI call-ins for HCWs. A password-protected version was posted on the hospital intranet and facilitated cohorting of infected patients. Additionally, it allowed timely discontinuation of the local mask rule on specific units, once 2 incubation periods concluded without new cases.

Funding: None

Disclosures: None