Antiviral use during influenza outbreaks in long-term care facilities

Abstract

Background: Influenza outbreaks (OBs) are common in long-term care facilities (LTCF) and can cause high morbidity and mortality. Outbreak control with antivirals is successful but problematic. I reviewed the Perth County experience with antivirals in LTCF OBs including the introduction of neuraminidase inhibitors (NI). Methods: Health department and facility records of all LTCF influenza OBs were reviewed including line listings, epidemic curves, laboratory studies, control measures, and antiviral dosing and side effects. Results: Amantadine prophylaxis was used in 29 LTCF influenza A OBs between 1989 and 2000. In 22 (76%) transmission stopped within 48–72 h but seven OBs (24%) were not controlled. Amantadine susceptibility testing in six OBs with amantadine failure showed emergence of resistant organisms in three and ongoing transmission of susceptible organisms in three. Amantadine failure was associated with simultaneous prophylaxis and treatment in the facility. Side effects were reported in 1.7% of residents and drug stopped in 0.7%. Attempts to limit amantadine use to only part of a facility were not successful. Logistical problems including delay in starting prophylaxis, inappropriate schedules, low staff uptake, knowing when to start or stop amantadine and treatment issues. In the 99/00 season, NI were used for persons with contraindications to amantadine, and for treating ill residents when amantadine prophylaxis was initiated for OB control (to prevent resistance). Switching residents to oseltamivir successfully stopped one OB that amantadine failed to control. Conclusions: Amantadine prophylaxis successfully controls most LTCF influenza A OBs but failures occur due to both resistant and sensitive viruses. NI have considerable potential in LTCF OBs.