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This award-winning blog supplements the articles in Hospital Infection Control & Prevention.

As Legionella Infections Surge, CDC Revises Healthcare Guidance

As Legionnaires disease (LD) hits record levels fueled by several recent national outbreaks, the Centers for Disease Control in Prevention is revising its guidelines on outbreak response for healthcare facilities, Hospital Infection Control & Prevention has learned.

Several issues appear to be on the table, including taking a more proactive approach by combining clinical and environmental surveillance findings, and possibly beginning outbreak investigations and water testing earlier based on a single confirmed infection.

A study presented this year at the CDC Epidemic Intelligence Service (EIS) conference showed that hospitals that intervene after one confirmed case of LD may detect and even prevent more subsequent cases. The study by Amanda Kamali, MD, a CDC EIS officer in Los Angeles, noted that the standard for hospitals in Europe is to conduct quarterly environmental culturing of water systems for Legionella. However, the CDC recommends that U.S. hospitals test water systems only during an outbreak of two or more cases or after one case in a transplant unit.1 In general, routine water testing in the absence of infections may not be cost-effective, as the CDC states on its website that “there is no evidence-based consensus recommendation regarding routine testing for Legionella for the prevention of legionellosis; as many research gaps exist. However, if testing is performed and Legionella is found, a plan should be in place regarding actions needed to eliminate Legionella from the water system.”2

The CDC is expected to align its forthcoming guidelines with the recently issued voluntary consensus standard to prevent legionellosis by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE).3 The CDC states that the ASHRAE standard applies to any inpatient healthcare facility including hospitals and long-term care facilities. It also applies to outpatient healthcare facilities as well as senior housing developments with or without on-site skilled nursing staff. The standard allows healthcare facilities to follow “an alternate path to compliance” that includes risk assessment for multiple organisms and clinical disease surveillance, the CDC noted.

“The CDC encourages healthcare facilities, to develop comprehensive water safety management plans,” Kamali says. “The newly released ASHRAE [standard] provides a framework for proactively managing building water systems and reducing the potential for Legionella colonization of these systems. Routine culturing of hospital water systems is not required. Some states and hospital systems in the U.S. do routine culturing, as do many European countries.”


1. Kamali A, Marquez P, Motala T, et al. Description of Nosocomial Legionella Infections: Los Angeles County. October 2005–August 2014. CDC EIS conference. Atlanta, April 20-23, 2015.

2. CDC. ASHRAE 188-2015: Legionellosis: Risk Management for Building Water Systems

3. ASHRAE 188 Legionellosis: Risk management for building water systems. June 26, 2015: