Legionellosis (Legionnaire's Disease)

Legionnaires’ disease (Legionellosis) is a bacterial infection of the lungs., and causes symptoms similar to pneumonia. Without treatment, illness can be severe or fatal.

The bacterium that causes Legionellosis is found naturally in freshwater environments like lakes and streams. It can become a health concern when it grows and spreads in human-made water systems like cooling towers, hot tubs that aren’t drained after each use, large plumbing systems, and other places that hold or process warm water. Air conditioning in homes and cars units do not use water to cool the air, so they are not a risk for growth of this bacteria.

• Centers for Disease Control and Prevention (CDC)

Hot Tub Displays and Legionella Risk

Hot tub displays at temporary events may pose a risk for Legionnaires’ disease, a type of pneumonia caused by inhaling mist containing Legionella bacteria.

The Centers for Disease Control and Prevention (CDC) is alerting environmental and public health practitioners about the public health need to maintain, clean and disinfect hot tubs properly to reduce potential exposure to Legionella. This guidance for environmental and public health practitioners can minimize risk for Legionella exposure from hot tub displays at temporary events (e.g., fairs, home and garden shows, conventions). Environmental health practitioners should work with event planners and hot tub vendors to minimize the risk of Legionella exposure even if the hot tub is only for display.

Guidance for Environmental and Public Health Practitioners

Legionella grows best in warm water (77°F–108°F), like the water temperatures used in hot tubs. Warm temperatures also make it hard to keep disinfectants, such as chlorine, at the levels needed to kill bacteria like Legionella. Disinfectant and other chemical levels in hot tubs should be checked regularly. Hot tubs should be cleaned as the manufacturer recommends.

A hot tub that is not adequately maintained can expose people to Legionella bacteria even if they do not get in it. This makes display hot tubs at temporary events a risk for Legionnaires’ disease if they contain Legionella bacteria. People with symptoms of Legionella exposure who have recent exposure to a hot tub filled with water should be encouraged to seek medical care.

Exposure to Legionella via aerosol or aspiration of water containing Legionella can lead to Legionnaires’ disease or Pontiac fever. Legionnaires’ disease is a severe type of pneumonia. Signs and symptoms can include cough, shortness of breath, muscle aches, headache, and fever. Most people get sick within 10 days of exposure, though the incubation period can be as long as 14 days. Pontiac fever symptoms are primarily fever and muscle aches; it is a milder illness than Legionnaires’ disease, and pneumonia is absent. Symptoms begin between a few hours to three days after being exposed to the bacteria and usually last less than a week.

Recommendations for Hot Tub Owners and Operators

Event planners and hot tub vendors should know about the risk that hot tubs pose when not maintained adequately, even if the hot tub is for display only. At vendor events where a hot tub is on display, the equipment vendor, display manager, or operator should:

1. Obtain operator and chemical handling training, if required by state or local authorities. National training courses are listed at the CDC’s Pool/Spa Inspector Training website.
2. Ensure that trained vendor staff are available at the display during operational hours.
3. Maintain free chlorine (2–4 parts per million or ppm) or bromine (4–6 ppm) levels continuously.
4. Maintain the pH level of the water at 7.2–7.8.
5. Test pH and disinfectant levels at least twice per day.
6. Maintain accurate records of disinfectant and pH measurements and maintenance activities.

At the end of each event, hot tub vendors should (in accordance with manufacturer's recommendations, where applicable):

1. Clean the hot tub.
2. Apply a biocidal shock treatment.
3. Drain it, removing as much water from the system as possible.
4. Remove filters.
5. Leave filters to dry.
6. Clean filters before reuse.
7. Replace filters when recommended by the manufacturer.
8. Protect the hot tub from external water sources (e.g., condensation drip, rain, humidity, moisture).
9. Keep the hot tub as dry as possible between events.