Legionnaires' disease is a bacterial disease commonly associated with water-based aerosols and often a result of poorly maintained air conditioning cooling towers and potable water systems. It occurs where water, contaminated with the legionella organism, is aerosolized and then breathed in by workers or patients. Legionnaires' disease is not contagious but is a potential environmental hazard. Consequently, only those who are directly exposed to a contaminated aerosolized water source can get the disease.
Healthcare facilities often have large, complex building water systems. They frequently undergo construction and plumbing changes. They often have aerosol-producing devices, like cooling towers, decorative fountains, and other devices unique to healthcare facilities (e.g., respiratory therapy equipment, hydrotherapy tubs, heater-cooler units). Patients in these settings often have risk factors for Legionnaires’ disease, such as advanced age, weakened immune systems, and chronic medical conditions.
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Legionella is a type of bacterium found naturally in freshwater environments, like lakes and streams. It can become a health concern when it grows and spreads in human-made building water systems like:
Although it is possible for legionella bacteria to grow in home plumbing systems, most outbreaks of the bacteria occur in large buildings with complex water systems.
After Legionella grows and multiplies in a building water system, water containing the bacteria spreads as droplets small enough for people to breathe in. People can get Legionnaires’ disease or Pontiac fever when they breathe in small droplets of water contaminated with the bacteria.
Less commonly, people can get sick by aspiration of drinking water containing Legionella. This happens when water accidently goes into the lungs while drinking. People at increased risk of aspiration include those with swallowing difficulties.
Most healthy people exposed to Legionella do not get sick. People at increased risk of getting sick are:
Legionella bacterial infections are usually treated with Erythromycin or a combination of Erythromycin and Rifampin. There are no vaccines that can prevent Legionnaires’ disease.
Legionellosis can present as two types of illness: Legionnaires’ disease and Pontiac fever. The two illnesses can be diagnosed with similar tests but are treated differently.
Legionnaires' disease is a severe form of pneumonia, requiring treatment with antibiotics to kill the harmful bacteria in the lungs. Most cases of this illness can be treated successfully. Healthy people usually get better after being sick with Legionnaires’ disease, but they often need care in the hospital.
Legionnaires' disease usually develops two to 10 days after exposure to legionella bacteria. It frequently begins with the following signs and symptoms:
By the second or third day, you'll develop other signs and symptoms that can include:
Although Legionnaires' disease primarily affects the lungs, it occasionally can cause infections in wounds and in other parts of the body, including the heart.
Possible complications of Legionnaires’ disease include:
When not treated promptly, Legionnaires’ disease can lead to death. About 1 out of every 10 people who gets sick with Legionnaires’ disease will die due to complications from their illness. For those who get Legionnaires’ disease during a stay in a healthcare facility, about 1 out of every 4 will die.
Pontiac fever symptoms are primarily fever and muscle aches; it is a milder infection than Legionnaires’ disease and resembles the flu. Symptoms begin between a few hours to 3 days after being exposed to the bacteria and usually last less than a week. Pontiac fever is different from Legionnaires’ disease because someone with Pontiac fever does not develop pneumonia.
Pontiac fever can produce the following symptoms:
Medical providers can use a urine or blood test to see if someone has Pontiac fever. However, a negative test doesn't completely rule out that someone does not have the illness. Clinicians most often diagnose Pontiac fever when there are other known laboratory-confirmed legionellosis cases (either Legionnaires’ disease or Pontiac fever) who may have been exposed to legionella at the same time or place. Pontiac fever goes away without specific treatment.
Legionella grows best in warm, stagnant water, like the water temperatures used in hot tubs. However, warm temperatures also make it hard to keep disinfectants, such as chlorine, at the levels needed to kill germs like Legionella. Disinfectant and other chemical levels in hot tubs should be checked regularly and hot tubs should be cleaned as recommended by the manufacturer.
Avoiding water conditions that allow Legionella bacteria to grow to high levels is the best prevention.
Specific preventive measures include:
Healthcare workers need to be aware that the bacteria can be present in water systems and promptly test vulnerable and/or symptomatic patients and use appropriate antibiotics quickly.
As mentioned earlier, Legionnaires' disease most frequently attacks individuals who have an underlying illness or weakened immune system. The most susceptible include persons who are elderly, smokers, and immunosuppressed.
How health department investigators respond to healthcare-associated cases and outbreaks of Legionnaires’ disease depends on the type and size of the healthcare facility, existing capacity of the facility and health department, and the number of cases. Public health officials should work closely with healthcare facility staff at each step in the process. The appropriate healthcare facility points of contact (e.g., administrator, infection preventionist, clinician, quality assurance representative, facility manager or engineer) may vary, depending upon the step.
In healthcare settings, public health officials and healthcare providers should consider Legionnaires’ disease as a possible diagnosis in any patient at risk for Legionnaires’ disease with healthcare-associated pneumonia (pneumonia with onset ≥48 hours after admission). This is especially important among patients with severe pneumonia (e.g., those requiring intensive care) or if you identify any of the following in a healthcare facility:
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