Duration of influenza outbreaks in long-term care facilities after antiviral prophylaxis initiation: Fraser Health, British Columbia, 2014-2017.

To assess the duration of antiviral prophylaxis (AP), we conducted a retrospective outbreak review over 3 seasons, looking for acute respiratory illness (ARI) onset after 5 days of AP. Of 114 facility-level outbreaks with 352 unit-level outbreaks, we found only 1 case of laboratory-confirmed influenza after 5 days of AP. New cases of ARI after 5 days of AP should be investigated, and recommendations for AP duration could be shortened to 7-8 days or less.