Legionella is a type of bacteria. It can live in fresh water. It can cause Legionnaires disease. This is a severe type of lung infection (pneumonia). This illness needs to be treated right away with antibiotic medicine. Legionella can also cause a milder illness called Pontiac fever.

Legionella doesn't spread from person to person. Instead, it can cause outbreaks of illness in places that have large water systems. It can overgrow where fresh water is sent through pipes and devices. This can happen if the water is not managed well. If the infected water is sprayed and a person breathes in water droplets, it can make them sick.

Legionella can grow in central water systems in places like these:

• Hotels
• Cruise ships
• Hospitals
• Large apartment buildings
• Office buildings
• Schools
• Industrial facilities

It can spread through spray and tiny water droplets from:

• Showers
• Fountains
• Hot tubs
• Humidifiers
• Air conditioning cooling towers
• Ice machines

Most healthy people don't get sick after contact with Legionella. But some factors can increase your risk of getting sick. These include:

• Being age 50 or older
• Smoking
• Having chronic obstructive pulmonary disease (COPD)
• Having a weak immune system due to cancer, diabetes, kidney failure, or other illnesses
• Taking medicine that makes your immune system weak

Symptoms can start 2 to 14 days after contact with the bacteria.

Symptoms of Legionnaires disease can include:

• Fever
• Tiredness
• Cough
• Shortness of breath
• Headache
• Body aches
• Upset stomach
• Diarrhea

Pontiac fever doesn't cause a lung infection. The symptoms include:

• Fever
• Headache
• Body aches
• Upset stomach
• Diarrhea

Your doctor will give you a physical exam. They will ask about your symptoms. They may ask if you've recently been in a place where Legionnaires disease is more of a risk, such as a hospital or hot tub, or areas experiencing cases.

You'll have an imaging test of your lungs. This may be a chest X-ray or CT scan. Your urine may be tested for the bacteria. You may need to cough up a sample of mucus from your lungs (phlegm) or be recommended to have a test of your lungs called a bronchoscopy. This can obtain a culture for the bacteria directly from your lungs. These samples are tested in a lab for the bacteria.

If you have Legionnaires disease, this is reported to the local health department. They will work to find the cause so that other people don't get sick.

Legionnaires disease is treated with antibiotic medicine. Most people who get sick need care in the hospital but make a full recovery. You may need to be treated in a hospital with IV medicine.

Pontiac fever most often goes away on its own.

Legionnaires disease can make you feel tired for months after you recover from it. Severe illness can cause breathing failure or organ failure. In some people, severe illness can lead to death.

There is no vaccine to protect against Legionella bacteria. Legionella growth in buildings can be prevented by good management of the water systems and devices that use water.

If you've been exposed to Legionella, contact your doctor right away if you have any of these:

• Fever of 100.4°F (38°C) or higher, or as directed by your doctor
• Chills
• Cough or shortness of breath
• Muscle aches
• Headache
• Confusion