The CDC investigations of 27 outbreaks of Legionnaires’ disease between 2000 and 2014 found health care-associated Legionnaires’ disease accounted for 33% of the outbreaks, 57% of outbreak-associated cases, and 85% of outbreak-associated deaths. Nearly all were attributed to water system exposures that could have been prevented by effective water management programs.
In 2015, CDC researchers analyzed surveillance data from 20 states and the New York City metropolitan area that reported > 90% of confirmed legionellosis cases to the Supplemental Legionnaires’ Disease Surveillance System. Of 2,809 reported cases, 553 were health care associated. Definite cases accounted for 3%, and possible cases accounted for 17% of all the cases reported. Although only a small percentage were definitely related to health care settings, the fatality rate was high at 12%.
Of the 85 definite health care-associated Legionnaires’ disease cases, 80% were associated with long-term care facilities. Of the 468 possible cases, 13% were “possibly” associated with long-term care facilities, 49% with hospitals, and 26% with clinics.
The CDC says the number of definite cases and facilities reported is “likely an underestimate,” in part because of a lack of Legionella-specific testing. Another explanation is that hospital stays are typically shorter than the 10-day period used in the analysis.
One-fourth of patients with definite health care-associated Legionnaires’ disease die. Health care providers play a critical role in prevention and response, the CDC says, by rapidly identifying and reporting cases. Legionnaires’ disease is “clinically indistinguishable” from other causes of pneumonia, the researchers note. The preferred diagnostic method is to concurrently obtain a lower respiratory sputum sample for culture on selective media and a Legionella urinary antigen test.
In health care facilities, the researchers say, “prevention of the first case of Legionnaires’ disease is the ultimate goal.” The best way to do that, they advise, is to have an effective water management program. Guidelines for developing and monitoring programs are available at https://www.cdc.gov/legionella/WMPtoolkit.