Temporal Trends in Risk Profiles and Outcomes of Non-Outbreak Legionellosis Cases in Georgia (2013-2023): A Sociodemographic and Regional Analysis Restricted; Files Only

Abstract

 

Legionellosis is typically associated with outbreaks, but a significant portion of cases occur sporadically, contributing to the overall disease burden. This study examines non-outbreak-associated legionellosis cases in Georgia from 2013 to 2023, focusing on disease trends, social vulnerability, and associated factors A total of 1,617 unique cases were reported, with 29% (n = 471) occurring among White, non-Hispanic or Latino males, primarily aged 50–65 years.

Case counts increased from 69 in 2013 to 199 in 2023. Average lag times between symptom onset and date of report to public health ranged from 19.1 days in 2013 to 8.4 days in 2019 with the highest calculated lag time being 48.7 days in 2020 during the COVID-19 pandemic. Brooks County, which had no reported incidence at the start of the study, reached 6.2 cases per 100,000 by the end of the period, while Fulton County experienced a 300% increase in incidence rates.

When examining the impact of social vulnerability, as measured by the Social Vulnerability Index (SVI), on legionellosis-related hospitalization or death, we found no significant association between higher SVI and hospitalization (Risk Ratio [RR] = 1.03, 95% CI: 0.87–1.22) or death (Odds Ratio [OR] = 1.92, 95% CI: 0.86–4.26) when controlling for age, occupation, and gender. However, we did find a statistically significant association between death and higher SVI when only controlling for age, with an odds ratio of 1.04 per year increase (95% CI: 1.03–1.06). These findings suggest that structural inequities, such as housing quality and healthcare access, may amplify risks for vulnerable populations.

Despite limitations, including missing data and possible geographic misclassification, the study underscores the importance of closer examination of social vulnerability on legionellosis risk and severity. Increased environmental monitoring, improved healthcare access, and public infrastructure investments are likely essential for reducing legionellosis risks. Furthermore, as climate change exacerbates environmental conditions favorable to Legionella growth, these efforts are crucial in mitigating future disease burdens and protecting vulnerable populations.

Table of Contents

Introduction.............................................................................................................................................................1-3

Methods...................................................................................................................................................................3-7

Results.....................................................................................................................................................................7-13

Table 1. Baseline Demographic Characteristics of Reported legionellosis Cases in Georgia, 2013–2023.............................8

Figure 1. Temporal trends in-non-outbreak legionellosis in Georgia (2013-2023)............................................................9

Figure 2. Annual Number of Non-Outbreak-Associated legionellosis Cases Reported in Georgia, 2013–2023....................10

Figure 3. Average Time from Symptom Onset to Case Entry in SENDSS, Georgia, 2013–2023...........................................11

Table 2. Number of Reported Comorbidities Among legionellosis Cases, Georgia, 2013–2023..........................................11

Table 3. Adjusted Odds Ratios for Death Due to legionellosis by SVI, Age, Gender, and Occupation, Georgia, 2013–2023...12

Table 4. Adjusted Odds Ratios for Hospitalization Due to legionellosis by SVI, Georgia, 2013–2023.................................13

Discussion................................................................................................................................................................13-15

Limitations................................................................................................................................................................15-16

Conclusion.................................................................................................................................................................16

References..................................................................................................................................................................17-21

About this Master's Thesis

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School	Rollins School of Public Health
Department	Epidemiology
Subfield / Discipline	Global Epidemiology - MPH & MSPH
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Health Sciences, Epidemiology
Keyword	Legionellosis Geographic disparities Non-outbreak cases Disease burden Social vulnerability
Committee Chair / Thesis Advisor	Chamberlain, Allison, Emory University

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