Legionnaires’ disease-associated hospitalizations significantly increased in the United States between 2006 and 2010, according to study results published in Open Forum Infectious Diseases.

In order to determine the burden and patterns of Legionnaires’ disease in the United States, researchers conducted a retrospective analysis using data from the National Hospital Discharge Survey (NHDS) from 2006 to 2010. The NHDS database provides estimates of inpatient hospitalization data from short-stay hospitals, excluding federal, military, and Veterans Administration hospitals.

Between 2006 and 2010, a total of 14,574 Legionnaires’ disease-associated hospitalizations were identified. The population-adjusted, annual incidence of Legionnaires’ disease-associated hospitalizations was 5.37 (95% CI, 5.12-5.64) in 2006; 7.06 (95% CI, 6.80-7.40) in 2007; 8.77 (95% CI, 8.44-9.11) in 2008; 17.07 (95% CI, 16.62-17.54) in 2009, and 9.66 (95% CI, 9.32-10.01) in 2010. The population adjusted incidence of Legionnaires’ disease-associated hospitalizations nearly doubled over the 5-year study period, with the highest incidence occurring in 2009.

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Individuals aged 39 years or younger had the lowest rate of Legionnaires’ disease-associated hospitalizations in all 5 years. With the exception of 2007 and 2009, men showed a significantly higher incidence rate compared with women.

A summer peak of Legionnaires’ disease-associated hospitalizations occurred from June through September in 2006, 2007, 2008, and 2010.

In 2009, notable spikes in the incidence of Legionnaires’ disease-associated hospitalization were observed in the Northeast (incidence rate [IR], 30.59; 95% CI, 29.18-32.06) and West (IR, 37.30; 95% CI, 36.01-38.71).

Study limitations include the use of the NHDS database, which is limited to inpatient hospitalization data and does not reflect the full scope of those who received treatment for Legionnaires’ disease, a lack of racial data reported in 42.2% of all hospitalizations, and an inability to determine the precise time and location of infection acquisition due to the nature of the available data. 

“The increasing disease burden of Legionnaires’ disease suggests that large segments of the US population are at risk for exposure to this waterborne pathogen,” especially in the “coming years due to aging of the US population, aging infrastructure, and changing climatic factors,” concluded the researchers.


Mudali G, Kilgore PE, Salim A, McElmurry SP, Zervos M. Trends in Legionnaires’ disease-associated hospitalizations, United States, 2006-2010 [published online July 17, 2020]. Open Forum Infect Dis. doi:10.1093/ofid/ofaa296

This article originally appeared on Infectious Disease Advisor