Association Between Sporadic Legionellosis and River Systems in Connecticut

• Published in: The Journal of infectious diseases 2018-01, Vol.217 (2), p.179-187
• Main Authors: Cassell, Kelsie, Gacek, Paul, Warren, Joshua L, Raymond, Peter A, Cartter, Matthew, Weinberger, Daniel M
• Format: Article
• Language: English
• Subjects: Editor's Choice; Major and Brief Reports
• ISSN: 0022-1899; 1537-6613
• DOI: 10.1093/infdis/jix531

Legionnaires’ disease has been on the rise over the last decade, and the determinants of nonoutbreak cases are not understood. We found that proximity to key river systems and watersheds was associated with increased disease incidence in surrounding zip codes. Abstract Background There has been a dramatic increase in the incidence of sporadic legionnaires’ disease in Connecticut since 1999, but the exact reasons for this are unknown. Therefore, there is a growing need to understand the drivers of legionnaires’ disease in the community. In this study, we explored the relationship between the natural environment and the spatial and temporal distribution of legionellosis cases in Connecticut. Methods We used spatial models and time series methods to evaluate factors associated with the increase and clustering of legionellosis in Connecticut. Stream flow, proximity to rivers, and residence in regional watersheds were explored as novel predictors of disease, while controlling for testing intensity and correlates of urbanization. Results In Connecticut, legionellosis incidence exhibited a strong pattern of spatial clustering. Proximity to several rivers and residence in the corresponding watersheds were associated with increased incidence of the disease. Elevated rainfall and stream flow rate were associated with increases in incidence 2 weeks later. Conclusions We identified a novel relationship between the natural aquatic environment and the spatial distribution of sporadic cases of legionellosis. These results suggest that natural environmental reservoirs may have a greater influence on the spatial distribution of sporadic legionellosis cases than previously thought.