Legionellosis in an infection caused by Legionella bacteria.
There are two different types of legionellosis:
- Pontiac fever
- Legionnaires' disease
Pontiac fever is a mild respiratory illness and Legionnaires' disease is more severe and is a type of pneumonia.
Legionnaires' disease is not normally spread from person to person.
Causes and Transmission
Legionella bacteria are found naturally in freshwater and moist environments (e.g., lakes, rivers, groundwater) worldwide. Legionella can become a public health problem in manmade water systems, where it can grow and spread, causing disease. Most healthy people who are exposed to Legionella do not become sick. However, people aged 50 years or older, smokers, and those with underlying medical conditions such as chronic lung disease, or those with a weakened immune system, are at higher risk of becoming sick from Legionella or with legionellosis.
Outbreaks of Legionnaires’ disease are most commonly associated with large or complex water systems (e.g., hospitals, long-term care facilities, hotels, cruise ships).
People can become sick when they breathe in mist from a water source that has Legionella (water used for showering, cooling towers, decorative fountains, and hot tubs). This CDC infographic helps illustrate how Legionella is spread.
Signs and Symptoms
Common signs and symptoms of legionellosis are:
- Muscle aches
- Loss of appetite
- Diarrhea (occasionally)
Contact your doctor if you develop symptoms, such as fever, cough, chills, or muscle aches. Be sure to mention if you spent any nights away from home in the last 10 days.
Treatment depends on whether or not the person has Pontiac fever or Legionnaires' disease. Pontiac fever requires supportive care only and will go away on its own. Legionnaires' disease is treated with antibiotics. Most people who get sick need care in a hospital but make a full recovery. However, about 1 out of 10 people who get Legionnaires’ disease die from the infection.
There are no vaccines against Legionella bacteria. To prevent Legionella bacteria from growing, it is important to make sure that water systems in buildings are being properly cared for and maintained.
How Common is Legionellosis?
Legionnaires’ disease is on the rise in Wisconsin and nationally. The rising trend may be related to a combination of factors, such as increased awareness and testing, more people at risk (e.g., aging population, use of immune-suppressing medication), and increased Legionella in the environment.
Because Legionnaires’ disease is likely underdiagnosed, the number of cases may be underestimated. More illness is usually found in the summer and early fall, but it can happen any time of year.
- Legionellosis Fact Sheet, P-42066 (Multiple Languages): Educational fact sheet for the general public on legionellosis covering signs and symptoms, treatment, and prevention
- About Legionellosis: CDC webpage including information on symptoms, diagnosis, possible causes of legionellosis, treatment, and prevention
- Legionellosis resources: CDC webpage containing resources for patients and their families
- How Legionella affects building water systems and people: CDC infographic illustrating how Legionella is spread
Reporting and Surveillance Guidance
This is a Wisconsin disease surveillance category II disease:
- Report to the patient's local public health department electronically, through the Wisconsin Electronic Disease Surveillance System (WEDSS), by mail or fax using an Acute and Communicable Disease case report, F-44151 (Word) or by other means within 72 hours upon recognition of a case.
- Information on communicable disease reporting
Wisconsin case reporting and public health follow-up guidelines:
- Update on Legionellosis – August 2018 Bureau of Communicable Diseases Monthly Webinar Series Presentation (Adobe Connect)
- Legionella Information for Clinicians (CDC)
- Laboratory Guidelines (CDC)
- Toolkit: Developing a Water Management Program to Reduce Legionella Growth and Spread in Buildings (CDC)
- Environmental Investigation Resources for Health Departments (CDC)