CDC Publishes Guidance on Reducing Growth and Spread of Legionella

Published June 8, 2016

Citing an alarming increase in the incidence of Legionnaires’ disease outbreaks, CDC yesterday released guidance intended to help building owners and managers prevent the conditions that lead to Legionella growth in water systems. The guidance, which CDC describes as a “toolkit,” is based on the recently revised ASHRAE standard Legionellosis: Risk Management for Building Water Systems and provides a checklist to help building managers identify whether a water management program is needed, examples of locations where Legionella could grow and spread in a building, and ways to reduce the risk of Legionella contamination.

“Years of outbreak response have taught us where to find Legionella hot spots,” said Nancy Messonnier, MD, director of CDC’s National Center for Immunization and Respiratory Diseases. “The toolkit will help building owners and managers better understand where those hot spots are and put measures in place to reduce the risk of Legionnaires’ disease.”

In comments (PDF) submitted to CDC in May, members of AIHA’s Indoor Environmental Quality Committee noted that the toolkit does not list AIHA’s Recognition, Evaluation, and Control of Legionella in Building Water Systems in its “resources” section. The committee also questioned CDC’s decision not to include information related to environmental sampling for Legionella, which is necessary to confirm that control measures are effective.

However, IEQ Committee member David Krause, a coeditor of the AIHA guideline, praised CDC for recognizing that building managers need additional tools to prevent and identify Legionella.

“We should be encouraged by the CDC’s engagement in Legionnaires’ disease prevention,” Krause said in an e-mail. “The toolkit is a good starting point for discussing the need for a water management plan.”

Krause, a toxicologist and industrial hygienist with Geosyntec Consultants in Tallahassee, Fla., noted that the toolkit aligns with ASHRAE’s Legionellosis standard, which does not address sampling.

“I believe that the hesitancy of public health agencies to rely upon sampling as the sole prevention strategy for Legionella in the past was driven by the absence of clear standards of care for professionals who collect and interpret samples,” Krause said. He added that the AIHA guidance, published last year, addresses this concern. “The guideline tightly binds sampling to validate Legionella control measures with a comprehensive water management plan based upon a risk assessment.”

In addition to the toolkit, CDC published a summary of recent Legionnaires’ disease outbreaks in North America. From 2000 through 2014 the rate of reported cases of legionellosis, which includes both Legionnaires’ disease and Pontiac fever, increased 286 percent, from 0.42 to 1.62 per 100,000 persons. CDC also cautioned that legionellosis may still be underreported.

The AIHA guideline Recognition, Evaluation, and Control of Legionella in Building Water Systems is available for purchase in the AIHA Marketplace. An article introducing the guideline appeared in the June/July 2015 issue of The Synergist.