Vital Signs: Health Care–Associated Legionnaires’ Disease Surveillance Data from 20 States and a Large Metropolitan Area — United States, 2015

Weekly / June 9, 2017 / 66(22);584–589

On June 6, 2017, this report was posted online as an MMWR Early Release.

Elizabeth A. Soda, MD1,2; Albert E. Barskey, MPH2; Priti P. Shah, MPH2; Stephanie Schrag, DPhil2; Cynthia G. Whitney, MD2; Matthew J. Arduino, DrPH3; Sujan C. Reddy, MD3; Jasen M. Kunz, MPH4; Candis M. Hunter, MSPH4; Brian H. Raphael, PhD2; Laura A. Cooley, MD2 (View author affiliations)

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Key Points

• Legionnaires’ disease is a severe lung infection caused by breathing in small droplets of water that contain Legionella bacteria. Persons aged ≥50 years, current or former smokers, and those with chronic diseases or a weakened immune system are at higher risk for Legionnaires’ disease.

• Legionella grows well in building water systems that are not adequately managed such as those in which disinfectant levels are low or water temperatures are warm. Effective water management programs are recommended to prevent Legionella growth in buildings with large or complex water systems, including health care facilities.

• The size and complexity of health care facility water systems might increase the risk for Legionella growth. Such health care facilities also provide care to persons who might be more susceptible to Legionnaires’ disease because of their underlying risk factors.

• Legionnaires’ disease continues to occur in U.S. health care facilities. Sixteen of the 21 U.S. jurisdictions, including 72 health care facilities in this analysis, reported definite health care–associated cases of Legionnaires’ disease.

• One fourth of persons with definite health care–associated Legionnaires’ disease die.

• Prevention and response requires coordination among health care facility leaders, health care providers, and public health professionals. Instituting and maintaining effective water management programs are the principal prevention measures. Rapid patient identification with appropriate laboratory testing and prompt intervention might prevent additional cases from occurring.

• Additional information is available at https://www.cdc.gov/vitalsigns.

On June 6, 2017, this report was posted online as an MMWR Early Release.

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Abstract

Background: Legionnaires’ disease, a severe pneumonia, is typically acquired through inhalation of aerosolized water containing Legionella bacteria. Legionella can grow in the complex water systems of buildings, including health care facilities. Effective water management programs could prevent the growth of Legionella in building water systems.

Methods: Using national surveillance data, Legionnaires’ disease cases were characterized from the 21 jurisdictions (20 U.S. states and one large metropolitan area) that reported exposure information for ≥90% of 2015 Legionella infections. An assessment of whether cases were health care–associated was completed; definite health care association was defined as hospitalization or long-term care facility residence for the entire 10 days preceding symptom onset, and possible association was defined as any exposure to a health care facility for a portion of the 10 days preceding symptom onset. All other Legionnaires’ disease cases were considered unrelated to health care.

Results: A total of 2,809 confirmed Legionnaires’ disease cases were reported from the 21 jurisdictions, including 85 (3%) definite and 468 (17%) possible health care–associated cases. Among the 21 jurisdictions, 16 (76%) reported 1–21 definite health care–associated cases per jurisdiction. Among definite health care–associated cases, the majority (75, 88%) occurred in persons aged ≥60 years, and exposures occurred at 72 facilities (15 hospitals and 57 long-term care facilities). The case fatality rate was 25% for definite and 10% for possible health care–associated Legionnaires’ disease.

Conclusions and Implications for Public Health Practice: Exposure to Legionella from health care facility water systems can result in Legionnaires’ disease. The high case fatality rate of health care–associated Legionnaires’ disease highlights the importance of case prevention and response activities, including implementation of effective water management programs and timely case identification.