Prevent Legionella

Safely reopening large buildings with complex plumbing

Building owners, building managers, and building operators

COVID-19 restrictions and safety measures led to closures and the limited use of buildings including schools, office facilities, and commercial sites. Low- or no-water use in vacant or underused buildings increases the risk to plumbing systems and the potential for Legionella.

As owners and maintenance staff reopen buildings, they should follow the safety guidance below to prevent Legionella and other opportunistic waterborne infections.

Where can building owners, managers and maintenance staff get help?

Building owners or maintenance staff who need technical assistance can email Steve Deem, P.E. at the state Department of Health, Office of Drinking Water.

Take free training on Legionella water management to ensure the safety of your staff and customers. Visit the Centers for Disease Control and Prevention to access additional information and the free training.

What is Legionella?

Legionella is a bacterium that occurs naturally in the environment, usually in water. Legionella can cause a type of pneumonia, called Legionnaires' disease and a flu-like illness called Pontiac Fever. People are exposed by breathing tiny water droplets contaminated with Legionella from water fixtures such as showers, hot tubs, and decorative fountains.

What are the symptoms of Legionnaires' disease?

Symptoms include cough, shortness of breath, muscle aches, headache, and fever.

Who is at greatest risk for Legionnaires' disease?

The risk of developing Legionnaires' disease is low, but it occurs more frequently in the elderly, those who smoke, and in individuals that are at higher risk of infection; such as those with a chronic illness, respiratory disease, or compromised immune system. The infection is caused by breathing in a mist or vapor containing the Legionella bacteria.

What is the treatment for Legionnaires' disease?

Legionnaires' disease is treated with antibiotics. Most people who get sick need hospitalization but make a full recovery. However, about 1 of 10 people who get Legionnaires' disease will die.

Is Legionnaire's disease common?

Most healthy people don't get Legionnaires' disease after exposure to Legionella. Risk factors like being 50 years or older, smoking, chronic lung disease, or a weakened immune system can increase a person's chances of getting sick.

Why is Legionella a concern now?

Many buildings are closed to the public or have limited access in order to help slow the spread of COVID-19. The resulting drop in building water use increases the risk for the formation of biofilm which supports Legionella growth in building plumbing and associated equipment like cooling towers, pools, decorative fountains, hot tubs and other equipment.

If Legionella grows during low-use periods, building users have a higher risk of contracting Legionnaires' disease and Pontiac Fever during the shutdown and when full use resumes.

Is there concern for Legionella when entering a building?

Most healthy people do not get Legionnaires' disease even after being exposed to Legionella. Legionella is a waterborne illness transmitted by inhaling contaminated freshwater droplets. Common sources can be cooling towers, showerheads and water features. The risk of getting sick from a building's water supply is low, especially for healthy people. There were 54 confirmed cases of Legionellosis reported in Washington in 2018.

Is there concern for Legionella at my kids' school?

The risk of getting Legionella from a building's water supply is very low, especially for children. School buildings would be at no higher risk than another building with a large plumbing system.

Does Legionella infection spread person to person?

The infection is caused by breathing in a mist or vapor containing Legionella bacteria. It is not contagious and almost never spreads from person to person.

Does this information apply to single family residential buildings?

No. The guidance on this page is for owners of larger buildings, building management companies, and building facility operators. While the principles addressed in these documents can apply to smaller plumbing systems found in private homes, the COVID-19 social distancing has not led to reduced water use in most single-family residences. Frequent water use in homes helps minimize conditions that promote Legionella growth.

What's the cutoff for a large building?

The guidance documents on this page are intended for larger structures with several floors and complex plumbing, or complexes serving multiple structures.

Where can I get more information about Legionnaire disease?

For information, resources, and links visit the Legionnaires' disease web page.