County-Level Influenza-Attributable Emergency Department Visits and Their Spatial Correlates in the United States:...

Area of Science:

• Epidemiology
• Public Health
• Environmental Health

Background:

• Seasonal influenza poses a significant public health challenge, yet its impact on emergency department (ED) visits is not fully understood due to data limitations.
• Quantifying influenza's burden on ED visits is crucial for effective resource allocation and public health interventions.

Purpose of the Study:

• To estimate county-level respiratory ED visits attributable to seasonal influenza.
• To investigate the spatial variations in influenza burden across different counties.
• To identify socioeconomic, environmental, and health-related factors associated with influenza burden.

Main Methods:

• Utilized daily hospital discharge records from California, Georgia, and New York (2005-2018) to assess community influenza activity.
• Employed quasi-Poisson time-series models to estimate influenza-attributable respiratory ED visit rates, controlling for temporal trends and environmental variables.
• Applied Bayesian spatial models to explore associations between influenza burden and county-level socioeconomic status, environmental exposures (PM2.5, humidity, temperature), and chronic disease prevalence.

Main Results:

• Influenza-attributable respiratory ED visit rates varied significantly by state, with Georgia (547/100,000) experiencing the highest burden, followed by California (232/100,000) and New York (226/100,000).
• Increased poverty and uninsured rates were associated with higher influenza burden. A 10% rise in these factors correlated with substantial increases in ED visit rates.
• Environmental factors like PM2.5, humidity, and temperature, along with chronic conditions (stroke, COPD, diabetes), showed positive associations with influenza-attributable ED visits, though these weakened after accounting for socioeconomic status.

Conclusions:

• Influenza-attributable respiratory ED visit rates display considerable spatial heterogeneity across counties.
• County-level socioeconomic factors, environmental exposures, and the prevalence of chronic diseases are significantly associated with the spatial distribution of influenza burden.