Trends in Legionnaires’ Disease-Associated Hospitalizations, United States, 2006–2010

BACKGROUND: Legionella pneumophila is a waterborne cause of both healthcare-associated and community-acquired pneumonia. Legionella pneumophila serogroup 1 is responsible for 80% of infections. There is currently limited published disease burden data on Legionnaires’ disease-associated hospitalization in the United States. METHODS: In this study, we estimated the annual incidence of Legionnaires’ disease-associated hospitalizations in United States and identified demographic, temporal, and regional characteristics of individuals hospitalized for Legionnaires’ disease. A retrospective study was conducted using the National Hospital Discharge Survey (NHDS) data from 2006 to 2010. The NHDS is a nationally representative US survey, which includes estimates of inpatient stays in short-stay hospitals in the United States, excluding federal, military, and Veterans Administration hospitals. All discharges assigned with the Legionnaires’ disease International Classification of Diseases 9th Clinical Modification discharge diagnostic code (482.84) were included in this study. RESULTS: We observed the annual incidence and number of Legionnaires’ disease-associated hospitalizations (per 100 000 population) in the United States by year, age, sex, race, and region. Over a 5-year period, 14 574 individuals experienced Legionnaires’ disease-associated hospitalizations in the United States The annual population-adjusted incidence (per 100 000 population) of Legionnaires’ disease-associated hospitalizations was 5.37 (95% confidence interval [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. A summer peak of Legionnaires’ disease-associated hospitalizations occurred from June through September in 2006, 2007, 2008, and 2010. CONCLUSIONS: Legionnaires’ disease-associated hospitalizations significantly increased over the 5-year study period. The increasing disease burden of Legionnaires’ disease suggests that large segments of the US population are at risk for exposure to this waterborne pathogen.