About Legionella (Legionnaires’ Disease)
Page last updated 8/2/2023.
See below, or click the following links, to learn more about:
Legionella are bacteria naturally found in freshwater environments, such as lakes and streams. The bacteria can become a health concern when they grow and spread in human-made building water systems like:
Showerheads and sink faucets
Cooling towers (structures that contain water and a fan as part of centralized air-cooling systems for buildings or industrial processes)
Decorative fountains and water features
Hot tubs
Hot water tanks and heaters
Large, complex plumbing systems
Small water droplets or mist from these sources can contain Legionella bacteria, which people can breathe in or inhale, and lead to an infection in the lungs. Severe infection with Legionella (also called “legionellosis”) is called Legionnaires’ disease. The milder form is called Pontiac fever.
Legionnaires’ disease is a very serious type of pneumonia (lung infection) caused by Legionella bacteria.
People can get Legionnaires’ disease when they breathe in small droplets of water in the air that have Legionella bacteria in them. Less commonly, people can catch the infection by accidentally getting water into the lungs while drinking, also known as aspiration.
In general, Legionnaires’ disease is not spread directly from one person to another.
Legionnaires’ Disease is very similar to other types of pneumonia (lung infection), with symptoms that may include:
- Cough
- Shortness of breath
- Fever
- Muscle aches
- Headaches
Legionnaires’ disease can cause other symptoms including diarrhea, nausea, and in severe cases, confusion. Symptoms usually being 2 to 14 days after being exposed to the bacteria.
People with Legionnaires’ disease have a serious type of pneumonia, which can be diagnosed by a chest x-ray. There are many types of infections that cause pneumonia. To find out if the pneumonia is caused by Legionella, there are two commonly used tests. These are a urine test and a test of phlegm from the lung.
Most healthy people exposed to Legionella do not develop Legionnaires' disease. People over the age of 50, current and former smokers, people with chronic lung disease, and people with weakened immune systems are at increased risk for Legionnaires' disease. Those that do get Legionnaires’ disease require treatment with antibiotics. Most people with this illness can be treated successfully, but they often need care in the hospital.
Possible complications of Legionnaires’ disease include lung failure and death.
The key to preventing Legionnaires’ disease is to reduce the risk of Legionella growth and spread.
Building owners and managers can use a water management program to reduce the risk of Legionella growing and spreading. Building water systems and devices that might grow and spread Legionella include showerheads and sink faucets, cooling towers (structures that contain water and a fan as part of centralized air-cooling systems for buildings or industrial processes), hot tubs, decorative fountains and water features, hot water tanks and heaters, and large, complex plumbing systems.
Legionnaires’ disease and Pontiac fever outbreaks occur when two or more people are exposed to Legionella in the same place and get sick at about the same time.
For additional outbreak related information, please visit:
For more information, contact the Epidemiology Unit at (619) 692-8499 or send us an e-mail.
Popular Services