In 2015, there were approximately 6,000 cases of Legionnaires’ disease reported, according to the CDC. Additionally, the rate of legionellosis cases reported quadrupled from 2000 to 2014. Because the disease is often underdiagnosed, this number is most likely an underestimate of the true number of cases. Legionella is bacteria that is naturally-occurring in fresh water aquatic systems and becomes a risk when it enters human-made water and plumbing systems. It thrives in warm water environments and is known to grow in hot tubs, spas, pools, fountains, ice machines, and faucets.

The Legionella bacteria was first discovered in 1976 in Philadelphia during an American Legion Convention. Many participants at the convention became ill with a type of pneumonia, which was later found to be caused by the respiration and inhalation of water droplets containing the Legionella bacteria.

The respiration or inhalation of water droplets or aerosols containing the bacteria can lead to community-acquired pneumonia, or Legionnaires’ disease along with Pontiac Fever which is a milder form of legionellosis that presents flu-like symptoms. There are over 60 species of Legionella, with six different serogroups that can cause disease in humans but most cases of legionellosis are caused by Legionella pneumophila serogroup 1, the pneumonic form of Legionella.


Environmental Health Significance

Because Legionella is a recently-emerging environmental health issue, the resources and materials available to address the concerns presented by the bacteria are insufficient. The significant increase in reported legionellosis cases over the last two decades results in a demand for more comprehensive public and environmental health programs to target the risks associated with Legionella. In addition, further education and training for public and environmental health professionals around building water systems and premise plumbing is necessary to develop programs for preventing and mitigating these risks.

NEHA is conducting a nationwide environmental scan of existing Legionella programs in health departments at both the local and state levels. NEHA would like to gain more information about current programs in place, the components of effective programs, and the resources and tools that programs are currently lacking. Ultimately, this information will be used to develop methods for best practices and to design a model Legionella program. A survey has been created to gather more information about Legionella programs. If you are a part of a health department or organization that addresses Legionella or has an interest in developing a program, please take NEHA’s Legionella program survey to aid us in our environmental scan. 


CDC Legionnaires' Disease Factsheet

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