Legionella & Legionnaires' Disease

What is Legionnaires' Disease?

Legionnaires' Disease is a serious type of pneumonia caused by Legionella bacteria. People can get sick when they breathe in mist or accidently swallow water into the lungs containing Legionella.

Causes, How it Spreads, and People at Increased Risk

Causes and Common Sources of Infection

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:

Showerheads and sink faucets
Cooling towers (structures that contain water and a fan as part of centralized air cooling systems for building or industrial processes)
Hot tubs that aren’t drained after each use
Decorative fountains and water features
Hot water tanks and heaters
Large plumbing systems
Home and car air-conditioning units do not use water to cool the air, so they are not a risk for Legionella growth.

How It Spreads

After Legionella grows and multiplies in a building water system, water containing Legionella then has to spread in droplets small enough for people to breathe in. People can get Legionnaires’ disease or Pontiac fever when they breathe in small droplets of water in the air that contain 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.

In general, people do not spread Legionnaires’ disease and Pontiac fever to other people. However, this may be possible under rare circumstances.

Talk to your doctor or local health department if:

You believe you were exposed to Legionella

AND

You develop symptoms, such as fever, cough, chills, or muscle aches

Your local health department can determine whether to investigate. Be sure to mention if you spent any nights away from home in the last 10 days.

People at Increased Risk

Most healthy people exposed to Legionella do not get sick. People at increased risk of getting sick are:

People 50 years or older
Current or former smokers
People with a chronic lung disease (like chronic obstructive pulmonary disease or emphysema)
People with weak immune systems or who take drugs that weaken the immune system (like after a transplant operation or chemotherapy)
People with cancer
People with underlying illnesses such as diabetes, kidney failure, or liver failure

Signs and Symptoms

People who get sick after being exposed to Legionella can develop two different illnesses: Legionnaires’ disease and Pontiac fever.

Legionnaires’ Disease

Legionnaires’ disease is very similar to other types of pneumonia (lung infection), with symptoms that include:

Cough
Shortness of breath
Fever
Muscle aches
Headaches

Legionnaires’ disease can also be associated with other symptoms such as diarrhea, nausea, and confusion. Symptoms usually begin 2 to 10 days after being exposed to the bacteria, but it can take longer so people should watch for symptoms for about 2 weeks after exposure.

If you develop pneumonia symptoms, see a doctor right away. Be sure to mention if you may have been exposed to Legionella, have used a hot tub, spent any nights away from home, or stayed in a hospital in the last two weeks.

Pontiac Fever

Pontiac fever symptoms are primarily fever and muscle aches; it is a milder infection than Legionnaires’ disease. 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 have pneumonia.

Diagnosis, Treatment, and Complications

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
Diagnosis

People with Legionnaires’ disease have pneumonia (lung infection), which can be confirmed by chest x-ray. Clinicians typically use two preferred types of tests to see if a patient’s pneumonia is caused by Legionella:

Urine test
Laboratory test that involves taking a sample of sputum (phlegm) or washing from the lung

Treatment and Complications

Legionnaires’ disease requires treatment with antibiotics (medicines that kill bacteria in the body), and 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.

Possible complications of Legionnaires’ disease include

Lung failure
Death

About 1 out of every 10 people who gets sick with Legionnaires’ disease will die due to complications from their illness.1 For those who get Legionnaires’ disease during a stay in a healthcare facility, about 1 out of every 4 will die.

Pontiac Fever
Diagnosis

Clinicians can use a urine or blood test to see if someone has Pontiac fever. However, a negative test doesn’t rule out that someone may have it (this is called a false negative). 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.

Treatment and Complications

Pontiac fever goes away without specific treatment.

Prevention

Water Management Programs

There are no vaccines that can prevent Legionnaires’ disease.

Instead, the key to preventing Legionnaires’ disease is to make sure that building owners and managers maintain building water systems in order to reduce the risk of Legionella growth and spread. Examples of building water systems that might grow and spread Legionella include:

Hot tubs
Hot water tanks and heaters
Large plumbing systems
Cooling towers (structures that contain water and a fan as part of centralized air cooling systems for building or industrial processes)
Decorative fountains

CDC developed a toolkit to help building owners and managers develop and implement a water management program to reduce their building’s risk for growing and spreading Legionella.

Legionella and Hot Tubs

Legionella grows best in warm 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. Learn how you can test the water before you use a hot tub and questions you should ask your hot tub operator to determine whether or not a hot tub has been properly maintained:

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