Legionnaires’ disease is a severe form of pneumonia caused by the Legionella bacterium. Outbreaks rarely – if ever – make national news. But that does not make it any less deadly. For example, the city of Flint, Mich., experienced 12 deaths from at least 80 detected cases of Legionnaires’ disease in 2014 and 2015. Bronx, New York, also suffered an outbreak during the summer of 2015. It was blamed for 12 deaths and 119 cases.

The U.S. Centers for Disease Control and Prevention (CDC) reports the number of people diagnosed with Legionnaires’ disease in the U.S. quadrupled between the years 2000 and 2014. Today, at least 5,000 people in the U.S. are diagnosed each year. At least 10 percent of cases result in death. The CDC believes a combination of factors is causing this increase. The U.S. has an aging population. There is a rise in chronic illness. Immune-system suppressing medications are being prescribed more often. And the nation’s failing water delivery systems are providing a breeding ground for Legionella bacteria.

What is Legionnaires’ disease?

Legionnaires’ disease was named in 1976 when American Legion members attending a convention in Philadelphia fell ill with pneumonia. CDC scientists identified that Legionella was the cause of the outbreak during one of the largest respiratory disease investigations in U.S. history.

Symptoms of Legionnaires’ disease are similar to other types of pneumonia. A person can experience coughing, headache, and fever. Muscle aches and shortness of breath are also common. Other symptoms may include nausea, diarrhea, and confusion. Legionella bacteria can also cause Pontiac fever, a milder infection without pneumonia. The treatment for Legionnaires' disease includes antibiotics and often hospitalization. Pontiac fever does not require medical care.

Legionella bacteria thrive in warm climates and naturally exist in freshwater environments, such as lakes and streams. The bacteria become a health issue when they are abundant in human water systems. Places at risk of growing and spreading the bacteria include:

• Cooling towers (air-conditioning systems for large buildings)
• Large plumbing systems
• Hot tubs and hot water heaters
• Decorative fountains
• Shower heads and faucets

Legionnaires’ disease prevention tips for the home

Take the following precautions to help limit the risk of Legionella exposure in the home:

• Set your water heater temperature to 140 degrees Fahrenheit. To learn more about setting your water heater temperature, visit www.osha.gov/dts/osta/otm/legionnaires/hotwater.html.
• Maintain your water heater properly. Find your hot water heater’s manufacturer’s instruction manual. Learn how often it should be cleaned and how to do it correctly.
• Perform hot-water flushes. Running faucets and shower heads for at least 30 minutes at 140 degrees Fahrenheit or more can help kill Legionella. Use caution. These temperatures can cause scalding.
• Maintain hot tubs carefully. Neglected hot tubs provide ideal conditions for growth and spread of Legionella. Learn more at www.cdc.gov/legionella/downloads/hot-tub-disinfection.pdf.
• Use humidifiers with caution. Learn more about humidifier safety here.

Legionnaires’ disease prevention tips for building managers

Building owners and managers can:

• Determine if their buildings are at risk of Legionella growth. Visit the CDC’s question and answer page to learn if your building is at risk – www.cdc.gov/legionella/maintenance/wmp-risk.html.
• Follow the industry standard for building water management. Learn more about ANSI/ASHRAE Standard 188-2015 – www.ashrae.org.
• Develop a water management program. Get the CDC’s 32-page toolkit – www.cdc.gov/legionella/maintenance/wmp-toolkit.

By lowering our exposure to Legionella and recognizing the possible signs of an infection, we can help protect our own health. We can also take steps as homeowners or commercial property managers to keep ourselves and others safe. Fortunately, Legionnaires’ disease is an illness of human error that is preventable.