Abstract
Legionnaires disease (LD) incidence is increasing in the United States. Health care facilities are a high-risk setting for transmission of Legionella bacteria from building water systems to occupants. However, the contribution of LD in health care facilities to national LD rates is not well characterized. To determine the burden of LD in US Department of Veterans Affairs (VA) patients and to assess the amount of LD with VA exposure. Retrospective cohort study of reported LD data in VA medical facilities in a national VA LD surveillance system from January 1, 2014, to December 31, 2016. The study population included total veteran enrollees and enrollees who used the VA health care system. The primary outcome was assessment of annual LD rates, categorized by VA and non-VA exposure. Legionnaires disease rates for cases with VA exposure were determined on both population and exposure potential levels. Rates by VA exposure potential were calculated using inpatient bed days of care, long-term care resident days, or outpatient encounters. In addition, types and amounts of LD diagnostic testing were calculated. Case and testing data were analyzed nationally and regionally. There were 491 LD cases in the case report surveillance system from January 1, 2014, to December 31, 2016. Most cases (447 [91%]) had no VA exposure or only outpatient VA exposure. The remaining 44 cases had VA exposure from overnight stays. Total LD rates from January 1, 2014, to December 31, 2016, increased for all VA enrollees (from 1.5 to 2.0 per 100 000 enrollees; P = .04) and for users of VA health care (2.3 to 3.0 per 100 000 enrollees; P = .04). The LD rate for the subset who had no VA exposure also increased (0.90 to 1.47 per 100 000 enrollees; P < .001). In contrast, the LD rate for patients with VA overnight stay decreased on a population level (5.0 to 2.3 per 100 000 enrollees; P < .001) and an exposure level (0.31 to 0.15 per 100 000 enrollees; P < .001). Regionally, the eastern United States had the highest LD rates. The urine antigen test was the most used LD diagnostic method; 49 805 tests were performed in 2015-2016 with 335 positive results (0.67%). Data in the VA LD databases showed an increase in overall LD rates over the 3 years, driven by increases in rates of non-VA LD. Inpatient VA-associated LD rates decreased, suggesting that the VA's LD prevention efforts have contributed to improved patient safety.
Highlights
Legionnaires disease (LD) is an acute pneumonia caused by Legionella species, primarily L pneumophila serogroup 1 in the United States.[1]
Data in the Veterans Affairs (VA) LD databases showed an increase in overall LD rates over the 3 years, driven by increases in rates of non-VA LD
Because inclusion of outpatient exposure was new in the 2014 Centers for Disease Control and Prevention (CDC) definitions for health care–associated (HCA) LD,[23,24] we examined the impact of the change on attribution of LD cases in the VA data set (Table 2)
Summary
Legionnaires disease (LD) is an acute pneumonia caused by Legionella species, primarily L pneumophila serogroup 1 in the United States.[1]. The result is an underappreciation for the burden of LD in the United States and missed opportunities for prevention. This is important for health care settings, which have occupants at risk for Legionella infection[11] and for which numerous outbreaks have been described.[2] The CDC recently reported health care–associated (HCA) LD surveillance data from 21 jurisdictions.[11] Of the 2809 confirmed LD cases reported in 2015, 3% were classified as definite HCA LD and 17% were classified as possible HCA LD, substantiating health care as a source for exposure. The general burden of HCA LD in the United States may not be well represented by passive surveillance systems
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