Legionnaires' Disease Outbreak Associated with a Cooling Tower at a Long-Term–Care Facility — Ohio, 2013

BACKGROUND:   On July 9, the Ohio Department of Health was notified of 2 long-term–care facility residents with Legionnaires’ disease (LD, a pneumonia resulting from inhalation of Legionella-contaminated water). We investigated to identify the outbreak source and prevent further cases.

METHODS:   On July 10, we requested all facility residents with respiratory symptoms be tested for Legionella. Local health departments assessed facility exposure among community LD cases. Outbreak cases were defined as pneumonia since May 1 with positive Legionella urine antigen test (UAT) or respiratory culture among persons who lived at, worked in, or visited the facility 2–10 days before symptom onset. We interviewed patients, assessed the environment, and cultured environmental samples. Positive cultures underwent serotyping, monoclonal antibody (MAb) testing, and sequence-based typing (SBT).

RESULTS:   We identified 39 LD cases; 6 patients died. Residents lived in 4 buildings; no common potable water source was identified. All patients were positive for Legionella pneumophila serogroup 1 (Lp1) by UAT. Among 15 patients with respiratory cultures, 14 were negative, and 1 was positive for Lp1. Water samples and swabs from a cooling tower serving 1 building and from another building’s potable water were positive for Lp1, both with matching MAb and SBT to the patient isolate; the patient had not been exposed to the potable water source. Six cases were identified among residents of a third building where no environmental Legionella was isolated. An electronic control system turned off cooling tower pumps during periods of low demand, preventing delivery of disinfectant by a timed-release system.

CONCLUSIONS:   A cooling tower relying on timed-release disinfection was the principal outbreak source. Tower maintenance should ensure adequate disinfection when using automated systems.