872 - Burden of Influenza Outbreaks in Long-Term Care Facilities in Philadelphia, 2012-2020

Background: In the United States, influenza and other acute respiratory viruses contribute to a high burden of disease in long-term care facility (LTCF) residents. We aim to characterize the disease patterns and inter-seasonal variation of influenza virus outbreaks in LTCFs and identify institutional, environmental, and public health interventions associated with differences in outbreak outcomes and characteristics.

Methods: We conducted a retrospective, longitudinal study of influenza outbreaks in LTCFs reported to the Philadelphia Department of Public Health (PDPH) over eight consecutive seasons (November 2012 through March 2020). Characteristics of individual outbreaks, facilities, and infection control measures were reported in the PDPH Influenza Outbreak database, while quality measures and other facility-level data were extracted from the CMS Nursing Home Compare (NHC) database. Cases of influenza-like illness (ILI) in residents and staff were reported.

Results: 131 influenza outbreaks were reported among 56 facilities, leading to 1196 cases of ILI, 227 influenza-related hospitalizations and 20 deaths. The median number of facility residents affected per outbreak was 4 (range, 0-52), and the resident attack rate was 3.0% (IQR, 1.6-7.4). Facility staff were affected in 56 (43%) of outbreaks. A greater number of facility beds was associated with sites reporting 3 or more outbreaks compared to those that did not (180 vs 133 beds, p=0.019). Public health measures were associated with lower total attack rates for surveillance (1.9% vs 4.3%, p=0.0015), education (1.9% vs 5.1%, p=0.0004), visitation restrictions (1.8% vs 3.1%, p=0.049), and vaccination policies of staff and/or residents (1.6% vs 2.7%, p=0.047). Smaller outbreaks were associated with the implementation of droplet precautions (3 vs 6, p=0.0071), antiviral treatment and prophylaxis (3 vs 6, p=0.024), and admission restrictions (4 vs 7, p=0.015).

Conclusion: Larger facility size was associated with an increased frequency of outbreaks. Public health measures may reduce the size and severity of influenza outbreaks in LTCFs. These results emphasize the importance of ensuring consistent utilization of recommended infection prevention strategies.