Legionnaire's Disease and the Legionella Pneumophila Bacterium

Legionnaire's disease is a form of pneumonia caused by the bacterium Legionella Pneumophila.

In 1976 a convention of the Pennsylvania American Legion was held at the Bellevue Stratford Hotel in Philadelphia. Over two hundred attendees became infected with pneumonia. Thirty-four people died. After examination of the lung tissue of the victims, a new bacterium was discovered. This new bacterium, the cause of the pneumonia outbreak, was named Legionella Pneumophila. The pneumonia was named Legionnaire's disease.

Legionnaire's disease is contracted by the inhalation of sprays, mists or microscopic droplets of water that are contaminated with the bacterium. Legionnaire's disease is not a contagious disease.

Legionella Pneumophila may live and flourish in almost any water system or equipment that distributes water as a spray or mist, including residential hot water heating systems. However, it is not likely that an individual would develop Legionnaire's disease from Legionella Pneumophila in their own home.

Legionella Pneumophila is much more likely to be found in substantial levels in the larger hot water heating systems of workplaces and public facilities such as hospitals, hotels and cruise ships. Legionella Pneumophila may also exist in the cooling towers of industrial cooling water systems, large central air conditioning systems, evaporative coolers, whirlpool spas and ice making machines.

In 1976, after inspection of the Bellevue Stratford Hotel, it was discovered that significant numbers of Legionella Pneumophila were present in the hotel's air conditioning system.

The most favorable environment for the growth of Legionella Pneumophila is warm stagnant water. The bacterium begin to increase in numbers at temperatures between 68°F and 122°F, with the optimum temperature range being between 90°F and 105°F. Rust and the presence of other microorganisms can also promote growth.

When water temperature is increased to 131 degrees F, Legionella Pneumophila will be killed in several hours. At temperatures above 158 degrees F, the bacterium is destroyed instantly. It is recommended that water systems should be operated at 140 degrees F.

Every year, between 10,000 and 50,000 people are infected with Legionella Pneumophila and contract Legionnaire's disease in the United States.

Initial symptoms of Legionnaire's disease include fever, headache, aching joints, lethargy and loss of appetite. After several days symptoms may increase in severity to high fever, coughing, difficulty in breathing, shortness of breath, chills and chest pains.

Individuals who are more susceptible to Legionella Pneumophila and Legionnaire's disease include those who have had organ transplants, those over seventy years of age, those infected with HIV, cancer patients and heavy smokers.