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.