Legionnaires' infection is the more severe form of the infection and produces pneumonia. Pontiac fever is caused by the similar bacterium, but produces a gently respiratory disease without pneumonia which looks like acute influenza.
Legionellosis is an infection that is caused by the bacterium Legionella pneumophila. These bacteria are found naturally in the environment and thrive in hot water and warm wet places. They are generally found in lakes, rivers, creeks, hot springs and other bodies of water. They can also be found in soil and potting mix. They do not seem to grow in car or window air-conditioners. An estimated 8,000 to 18,000 people get legionellosis in the United States each year. Infections have been traced to mist-producing devices, such as certain air-conditioning systems. Legionellosis takes two distinct forms.
People of any age can get legionellosis but the disease most often affects the elderly. People with underlying illnesses such as cancer or those with lowered immune system resistance to disease are also at higher risk. It rarely occurs in otherwise healthy people. The most common symptoms of legionellosis are fever, chills, and a cough. The cough may either be dry or produce sputum.
Several patients also have muscle aches, headaches, fatigue, loss of appetite and, rarely, diarrhea. These symptoms usually begin 2 to 14 days after being exposed to the bacteria. Legionnaires' disease can be very grave and can cause death in up to 5% to 30% of cases. Legionnaires' disease is treated with antibiotics. The antibiotics used most often have been levofloxacin and azithromycin. Macrolides are used in all age groups while tetracyclines are prescribed for children above the age of 12 and quinolones above the age of 18. Erythromycin is currently recommended as the drug of choice.
Pontiac fever requires no exact treatment. Prevention of legionellosis is based upon proper maintenance of heating, cooling and plumbing systems. Smoking is an important risk factor for developing symptomatic infection in those exposed to Legionella bacteria, and it is presumed cessation of smoking reduces an individual's risk of infection. Persons with hot tubs and whirlpool baths should take special care to keep them clean and free of Legionella bacteria. To minimize the risk of infection through potting mix gardeners should be advised to wear gloves and wash hands after handling potting mix even if gloves have been worn.
