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BACKGROUND: During June‒October 2014, the North Carolina (NC) Division of Public Health identified 5 outbreaks of Legionnaires’ disease (LD), a waterborne infection, at different long-term care facilities (LTCFs). Before June 2014, the last LTCF-related LD outbreak in NC occurred in September 2004. We reviewed the 5 investigations to assess Legionella remediation strategies and time from outbreak identification to demonstration of Legionella eradication.
METHODS: An LTCF-related LD outbreak was defined as ≥2 LD cases (radiologic-confirmed pneumonia and a positive Legionella urine antigen test) occurring during a 6-month period among persons with exposure to the same LTCF 2‒10 days before illness onset. Each LTCF collected representative environmental bulk water and swab samples for Legionella culture initially and after remediation until all environmental samples were Legionella-negative. Subsequently, environmental samples were collected routinely for 6 months to ensure Legionella eradication. We summarized environmental assessments and remediation efforts and outcomes. We evaluated Legionellaculture results from environmental samples taken before and after remediation.
RESULTS: We identified 23 LD cases among 5 LTCF-related LD outbreaks; median cases per outbreak was 3 (range: 2‒8). Each LTCF had water system conditions favorable for Legionella amplification, including areas of stagnation and suboptimal hot water temperatures; none had a health care facility Legionella prevention plan. Upon outbreak identification, each LTCF implemented water restrictions until recommended 0.2-µm point-of-use filters were installed and an environmental engineer was hired to address amplification conditions. Legionella was isolated from initial environmental samples taken at 4 of 5 LTCFs. Of these 4, Legionella eradication was achieved after 1-time water system superheating at 1 (25%) LTCF and after 2 rounds of superheating and hyperchlorination at 1 (25%) LTCF. Time from outbreak identification to demonstration of persistent Legionella eradication at these LTCFs was 4 weeks and 13 weeks, respectively. Despite remediation and engineering efforts, Legionella was persistently isolated from subsequent environmental samples at 2 LTCFs (50%); 1 performed 1-time superheating, and 1 performed 1-time superheating and hyperchlorination. Control measures remain in place at these 2 LTCFs until Legionella eradication is complete. The LTCF with initial Legionella-negative environmental samples conducted 1-time superheating; routinely collected environmental samples have been Legionella-negative.
CONCLUSIONS: Standard remediation and engineering efforts achieved Legionella eradiation over 4‒13 weeks at 2 LTCFs where Legionella was isolated from initial environmental samples. However, low-level Legionella contamination persisted at 2 LTCFs despite similar efforts; complete Legionella eradication might require secondary disinfection or other protracted remediation strategies at these facilities.