Legionnaires' disease

A type of pneumonia caused by Legionella bacteria

Legionella pneumophila, the bacterium responsible for Legionnaires' disease

Legionnaires' disease is a severe form of pneumonia—lung inflammation usually caused by infection. It is caused by a bacterium known as Legionella pneumophila. The disease is named after an outbreak in 1976 at an American Legion convention in Philadelphia.

Signs and symptoms

The symptoms of Legionnaires' disease are similar to those of other types of pneumonia. They can include cough, shortness of breath, fever, muscle aches, and headaches. These symptoms usually begin 2 to 10 days after exposure to the bacteria. In some cases, people may also experience nausea, vomiting, and diarrhea.

Causes

Legionnaires' disease is caused by the bacterium Legionella pneumophila. This bacterium is found naturally in freshwater environments, like lakes and streams. However, it can become a health concern when it grows and spreads in human-made water systems such as:

• Cooling towers of air conditioning systems
• Hot water tanks and heaters
• Large plumbing systems
• Decorative fountains

Cooling system water, a common source of Legionella bacteria

Transmission

The bacteria are transmitted through the inhalation of aerosolized water droplets containing Legionella. This can occur in showers, hot tubs, or air conditioning systems in large buildings. It is not spread from person to person.

Diagnosis

Diagnosis of Legionnaires' disease is typically confirmed by a combination of clinical symptoms and laboratory tests. These tests may include:

• Urinary antigen test
• Sputum culture
• Blood tests

Treatment

Legionnaires' disease is treated with antibiotics. The most commonly used antibiotics include macrolides and fluoroquinolones. Early treatment is crucial to prevent complications.

Severe pneumonia caused by Legionella pneumophila

Prevention

Preventing Legionnaires' disease involves maintaining and cleaning water systems to prevent the growth of Legionella. This includes:

• Regular cleaning and disinfection of cooling towers
• Maintaining appropriate water temperatures
• Preventing water stagnation

Epidemiology

Legionnaires' disease can occur as a single case or as part of an outbreak. Outbreaks are often associated with large or complex water systems, such as those found in hospitals, hotels, and cruise ships.

History

The disease was first identified in 1976 following an outbreak at the Bellevue-Stratford Hotel in Philadelphia, where members of the American Legion were attending a convention. The outbreak resulted in 34 deaths and over 200 cases of illness.

Diagram of the pathogenesis of Legionnaires' disease

Related pages

• Pneumonia
• Bacterial infections
• Public health