Accepted for/Published in: JMIR Public Health and Surveillance
Date Submitted: Aug 23, 2025
Date Accepted: Nov 11, 2025
Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.
County-Level Influenza-Attributable Emergency Department Visits and their Spatial Correlates in the United States
ABSTRACT
Background:
Burden of seasonal influenza on emergency department (ED) visits is poorly quantified due to case ascertainment and data availability challenges. This study estimates county-level respiratory ED visits attributable to influenza using time-series models and examines spatial heterogeneity in county-level burden in three states.
Objective:
To estimate county-level seasonal influenza–attributable emergency department (ED) visit rates and examine their associations with socioeconomic, environmental, and chronic health covariates in three US states (California, Georgia, and New York).
Methods:
We used daily hospital discharge records to measure community-level influenza activity in California (2005–2018), Georgia (2010–2018), and New York (2005–2018). County-level influenza-attributable respiratory ED visit rates were estimated using quasi-Poisson time-series models that adjusted for temporal trends and environmental factors. Under a meta-regression framework, Bayesian spatial hierarchical models were then applied to evaluate associations between ED visit rates and county-level socioeconomic status (SES), environmental exposures, and chronic health conditions.
Results:
Influenza-attributable respiratory ED visit rates per 100,000 population were 226 (95% CI: 206, 246) in New York, 232 (95% CI: 206, 259) in California, and 547 (95% CI: 506, 589) in Georgia. A 10% increase in county-level poverty and uninsured rates were associated with higher influenza burden, increasing influenza-attributable respiratory ED visit rates by 160 (95% CrI: 127, 196) and 217 (95% CrI: 168, 265), respectively. Long-term PM2.5, humidity, and temperature also exhibited positive associations. Chronic conditions also increased ED visit rates by 1,476/100,000 (95% CrI: 1,167, 1,778), 588/100,000 (95% CrI: 400, 747), and 488/100,000 (95% CrI: 402, 574) per 10% increase in stroke, chronic obstructive pulmonary disease, and diabetes prevalence, respectively. These associations weakened after adjusting for SES.
Conclusions:
Influenza-attributable respiratory ED visit rates exhibit significant spatial heterogeneity that is associated with county-level socioeconomic factors, environmental exposures, and chronic disease prevalences.
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