Containing influenza outbreaks with antiviral use in long‐term care facilities in Taiwan, 2008‐2014

BACKGROUNDS Influenza can spread rapidly in long-term care facilities (LTCFs), and residents are usually at higher risk for influenza infections. OBJECTIVE Our study aimed to evaluate the effectiveness of antiviral interventions on outbreak control. METHODS Taiwan Centers for Disease Control used a syndromic surveillance system to monitor outbreaks in LTCFs. Local public health authorities verified those outbreaks and logged reports to the Epidemic Investigation Report Files Management System (EIRFMS). We conducted a retrospective cohort study by reviewing EIRFMS reports of influenza outbreaks in LTCFs during 2008-2014. An influenza outbreak was defined as 3 or more cases of influenza-like illness occurring within a 48-hours period with ≥1 case of real-time RT-PCR-confirmed influenza in the same LTCF. Antiviral interventions included providing antiviral treatment for patients and antiviral prophylaxis for contacts during outbreaks. RESULTS Of 102 influenza outbreaks, median days from onset of the first patient to outbreak notification was 4 (range 0-22). Median attack rate was 24% (range 2.2%-100%). Median influenza vaccination coverage among residents was 81% (range 0%-100%); 43% occurred during the summer months. Even though antiviral treatment was provided in 87% of the outbreaks, antiviral prophylaxis was implemented in only 40%. Starting antiviral treatment within 2 days of outbreak onset was associated with keeping attack rates at <25% (OR 0.29, 95% CI: 0.12-0.71). CONCLUSIONS Early initiation of antiviral treatment may reduce the magnitude of influenza outbreaks. Clinicians should identify patients with influenza and start antiviral use early to prevent large outbreaks in LTCFs.