Legionella and Legionnaires' Disease

Legionella bacteria causes Legionnaires’ disease. In nature, legionella bacteria live in freshwater and rarely cause illness. Getting sick from these bacteria is rare, but possible when water is aspirated into the lungs. Most healthy people do not get Legionnaires’ disease after being exposed to Legionella. Current or former smokers, those who suffer from lung disease such as COPD, and those who have a weakened immune system have greater susceptibility.

Breathing in legionella from water is the only way to get Legionnaires’ Disease. It is not contagious, and cannot pass from person to person. If water systems are not properly maintained, legionella bacteria can grow and spread. When small water droplets are aerosolized – for example, during showers, washing a car, using hot tubs or decorative fountains, or power washing – legionella bacteria could be inhaled.

If water systems are not properly maintained, legionella bacteria can grow and spread. Conditions that promote its growth include water temperature, stagnant water, and sediment.

To reduce legionella growth and the danger of Legionnaires’ Disease, hot water heaters should be set to a minimum of 120⁰F. This temperature can also reduce the potential for scalding (hot water burns). Faucets or showers that do not get used at least weekly should be flushed by running the water for three minutes. For a full list of recommendations from the State. please click here.

If the temperature is set to greater than 120⁰ F, make sure you take extra precautions to mix cold and hot water at the faucet and shower to avoid scalding. If you have household members at increased risk of scalding, such as young children or older adults, you may consider installing a thermostatic mixing valve. A mixing valve allows your water to be stored at a higher temperature within your water heater to help kill bacteria while eliminating concerns about water being too hot at sinks or showers. If you decide to install a mixing valve, be sure to follow the manufacturer’s instructions for routine cleaning and maintenance to avoid bacteria growth within the valve.

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NJ Department of Health


preventing legionnaires disease
legionnaires disease info from the cdc