Legionnaires Disease
Legionnaires Disease

Legionnaires Disease 

What Legionnaires' disease is
Where Legionella bacteria is found
Health effects associated with Legionnaires' disease
Decreasing exposure to Legionella bacteria

What Legionnaires' Disease Is 

In 1976 at an American Legion convention held at the Bellevue-Stratford Hotel in Philadelphia, 182 Legionnaires developed pneumonia and 29 died from what was then an unknown disease. Eventually, the bacterium that was responsible for the disease was isolated and named Legionella pneumophila, and the disease associated with it became known as Legionnaires' disease. The source of this particular bacterium was finally discovered to be the hotel's ventilation and humidification system.

According to the Centers for Disease Control and Prevention (CDC), an estimated 8,000 to 18,000 people get Legionnaires' disease in the United States each year. Though it is the outbreaks of this disease that gets media attention, most cases are isolated ones. If outbreaks do happen, they usually occur in the summer or early fall, though the disease can occur at any time of the year.

Some people can be infected with the Legionella bacterium and have mild symptoms or no illness at all. There are about 35 different Legionella species known to produce two distinct illnesses, Legionnaires' disease and Pontiac fever. Legionnaires' disease is a severe pneumonia in which 5 percent to 30 percent of those affected die. The incubation period is from 2 to 10 days. Pontiac fever is a mild, non-pneumonia influenza-like illness with an incubation period of approximately 36 hours. It is not clear why the same type of bacterium can produce such different illnesses. 

Sources of Legionella Bacteria 

Legionella bacteria are found in half of bodies of water in the U.S., but they especially thrive in a warm and humid environment. They can survive for several months in a wet environment and multiply in the presence of algae and organic matter. If circulated air picks up droplets of contaminated water from the cooling tower of a building ventilation system, the bacteria can be transported throughout the building. That is why ventilation systems get the most attention in terms of Legionella bacteria.

Places where Legionella has been found include:

  • Air humidifiers

  • Air-conditioning cooling towers (but not window air-conditioners or car air-conditioning units)

  • Warm water supplies

  • Showerheads: this is especially true in hotels where it is possible to inhale aerosolized Legionella from taking a shower. Because hotels limit the temperature of the hot water to keep from scalding guests, the Legionella is not killed.

  • Water faucets, including residential tap water

  • Plumbing systems

  • Hot water heaters

  • Potting soil: infections with Legionella longbeachae have been associated with gardening and use of potting soil in Australia and Japan and was just reported in the US in June 2000. This was the first time such a transmission from potting soil had occurred in the United States. One victim of Legionella longbeachae infection was a 46-year-old woman who had been hospitalized in Washington State with pneumonia. The patient reported that she had been potting plants during the 10 days before her symptoms began in May. Another woman in Oregon had also been potting plants in a home garden using commercial potting soil mixtures 10 days before her symptoms began in April.1

  • Decorative fountains

  • Respiratory therapy equipment

  • Whirlpool baths or spas: in 1996 a whirlpool spa display at a home improvement store in Virginia was the source of infection for 14 people hospitalized with Legionnaires disease. In contrast with other spa- or whirlpool-associated outbreaks, in this outbreak, none of the people who got Legionnaires' disease actually entered the water. Instead, all were exposed only by walking by or spending time in the area surrounding the spa.2

  • Grocery store vegetable misters

Health Effects Associated With Legionnaires' Disease

Legionella bacteria must reach the lungs in order to produce the disease. This comes from inhaling small particles of contaminated water (aerosols) or soil. Legionella is not spread from person to person.

Not everybody infected with Legionella will develop Legionnaires disease. There are some factors that make some people more at risk for developing the disease than other people. These risk factors are:

  • Age over 50 years (though the disease has been reported in all age groups)

  • Suppression of the immune system (those whose resistance to infection is reduced) such as occurs with cancer, AIDS, or chronic kidney disease

  • Smoking

  • Alcohol abuse

  • Diabetes

The disease may not appear until 2-12 days after an exposure. Common symptoms that may be seen with Legionnaires' disease include:

  • Headache

  • Muscle aches and pains

  • High fever (up to 104°F to105°F)

  • Shaking chills

  • Cough—usually begins on the second or third day and may be dry or may produce sputum

  • Fatigue

  • Loss of appetite

  • Nausea/vomiting

  • Diarrhea (occasionally)

  • Mental changes, such as confusion, disorientation, hallucination and loss of memory, can occur to an extent that seems out of proportion to the seriousness of fever.

    Complete recovery can take several weeks. The antibiotics that are commonly used to treat Legionnaires' disease are erythromycin and rifampin.

Decreasing Exposure to Legionella Bacteria

  • Inspect and thoroughly clean cooling towers and evaporative condensers at least once a year.

  • Add a disinfectant, such as chlorine, into cooling towers and other water reservoirs.

  • Remove any algae and accumulated scale from air and water handling systems.

  • Air filters should be examined, cleaned and/or replaced periodically and tested for leaks.

  • Fresh air intakes should not be built close to cooling towers since contaminated aerosols may enter the ventilation system.

  • Cooling towers should be positioned so the drift or evaporate does not enter the fresh air intake.

  • Hot water tanks should be cleaned regularly.

  • The water system should be flushed out on a regular basis to prevent the water from stagnating.

  • Clean home humidifiers in accordance to manufacturers' instructions

References

  1. Duchin JS, et al. Legionnaires' Disease associated with potting soil?California, Oregon, and Washington, May-June 2000. MMWR. September 01, 2000;49(34):777-778.

  2. Hershey J, et al. Legionnaires' disease associated with a whirlpool spa display?Virginia, September-October, 1996. MMWR. January 31, 1997;46(04):83-86.