Legionnaires’ disease is also known as legionellosis. It is a form of atypical pneumonia caused by any type of Legionella bacteria.
Legionella is a type of bacterium found naturally in freshwater environments, like lakes and streams. It only become a health concern when it grows and spreads in human-made building water systems like:
- Showerheads and sink faucets
- Cooling towers
- Hot tubs that aren’t drained after each use
- Decorative fountains and water features
- Hot water tanks and heaters
- Large plumbing systems
Legionellosis varies in severity from a mild febrile illness to a serious and sometimes fatal form of pneumonia.
Legionnaires’ disease transmission
The most common form of transmission of Legionella is inhalation of contaminated aerosols. Sources of aerosols that have been linked with transmission of Legionella include air conditioning cooling towers, hot and cold water systems, humidifiers and whirlpool spas. Infection can also occur by aspiration of contaminated water or ice, particularly in susceptible hospital patients, and by exposure of babies during water births.
There is no direct human-to-human transmission.
The length of time between exposure to the bacteria and the appearance of symptoms is generally 2–10 days, but can rarely extend to as long as 20 days. For the general population, among those exposed, between 0.1 and 5.0% develop the disease, while among those in hospital, between 0.4 and 14% develop the disease.
Signs and symptoms
Those with Legionnaires’ disease usually have fever, chills, and cough which may be dry or may produce sputum.
Almost all experience fever, while around half have cough with sputum, and one-third cough up blood or bloody sputum.
Some also have muscle aches, headache, tiredness, loss of appetite, loss of coordination (ataxia), chest pain, or diarrhea and vomiting. Up to half of those with Legionnaires’ disease have gastrointestinal symptoms, and almost half have neurological symptoms, including confusion and impaired cognition. “Relative bradycardia” may also be present, which is low or low-normal heart rate despite the presence of a fever.
Not everyone exposed to legionella bacteria becomes sick. You’re more likely to develop the infection if you:
- Smoke: Smoking damages the lungs, making you more susceptible to all types of lung infections.
- Have a weakened immune system as a result of HIV/AIDS or certain medications, especially corticosteroids and drugs taken to prevent organ rejection after a transplant.
- Have a chronic lung disease such as emphysema or another serious condition such as diabetes, kidney disease or cancer.
- Are 50 years of age or older.
- People with cancer
- People with underlying illnesses such as diabetes, kidney failure, or liver failure.
Occupations at risk for Legionnaires’ disease?
Workers most at risk are those with occupations that require them to work in sealed buildings including those workers who maintain water cooling towers in air conditioning systems.
Some outdoor occupations may be considered at risk as well. Soil disturbed in areas where surface or aerosolized water discharge occurs has the potential to cause exposure to the microorganism.
In a few cases, the Legionella bacteria from cooling towers has survived and spread into the air for distances of several kilometers.
Outbreaks of legionnaires’ disease are preventable, but prevention requires meticulous cleaning and disinfection of water systems, pools and spas.
Avoiding smoking is the single most important thing you can do to lower your risk of infection. Smoking increases the chances that you’ll develop legionnaires’ disease if you’re exposed to legionella bacteria.
Some specific ways of prevention are:
- Keep water temperature either above or below the 20–50 °C (68–122 °F) range in which the Legionella bacterium thrives.
- Prevent stagnation, for example, by removing from a network of pipes any sections that have no outlet (dead ends). Where stagnation is unavoidable, as when a wing of a hotel is closed for the off-season, systems must be thoroughly disinfected just prior to resuming normal operation.
- Prevent the buildup of biofilm, for example, by not using (or by replacing) construction materials that encourage its development, and by reducing the quantity of nutrients for bacterial growth that enter the system.
- Periodically disinfect the system, by high heat or a chemical biocide, and use chlorination where appropriate. Treatment of water with copper-silver ionization or ultraviolet light may also be effective.
- System design (or renovation) can reduce the production of aerosols and reduce human exposure to them, by directing them well away from building air intakes.
How to diagnose the disease
- Blood test
- Chest X-ray
- CT scan
If you feel you have been exposed to the disease, visit a doctor for diagnosis and treatment.
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