Information for the General Public
What is legionella?
Legionella is a type of bacteria naturally found in freshwater environments as well as human-made water systems including but not limited to hot tubs, decorative fountains, and/or cooling towers. Legionella can cause legionnaire's disease, a serious type of pneumonia infection, or Pontiac fever, a more mild respiratory illness.
What are symptoms of legionnaire's disease?
Although Legionella can cause serious infections, most healthy people who are exposed to Legionella don’t get sick. It usually takes 2 to 14 days after being exposed to Legionella. Symptoms may include:
- Cough
- Shortness of breath
- Fever
- Chills
- Muscle aches
- Headaches
How can legionnaire's disease spread?
Small water droplets or mist from freshwater sources including hot tubs, decorative fountains, and/or cooling towers can contain Legionella bacteria, which people can breathe in without knowing. Legionnaire’s disease does not spread from person to person.
Resources
Information for Healthcare Providers
Legionnaires' disease is characterized by illness with pneumonia diagnosed radiographically or clinically. Clinical symptoms may vary but include acute onset of lower respiratory illness with fever or cough.
Risk factors
- Over the age of 50 years
- Chronic lung disease
- Immunocompromised
- Smoking
Reporting
Legionellosis is reportable in Orange County within seven calendar days of identification. To report a case, health care providers/facilities should contact Communicable Disease Control Division at (714) 834-8180 or fax reports to (714) 560-4050.
Laboratory testing
Recommended testing for Legionnaires’ disease includes PCR or culture of lower respiratory specimens and urine antigen. Lower respiratory specimens should ideally be obtained prior to start of antibiotics or as soon as possible after treatment has started. The urine antigen test can detect Legionella infections in some cases for days to weeks after treatment. Urine antigen testing detects Legionella pneumophila serogroup 1, the most common cause of Legionnaires’ disease.
Resources
- CDPH: Information for Health Professionals and Clinical Laboratories
- CDC: Clinical Guidance for Legionella Infections
- CDC: What Clinicians Need to Know about Legionnarie's Disease
Frequently Asked Questions
- Legionnaires’ Disease – Frequently Asked Questions (English)
- Legionnaires’ Disease – Frequently Asked Questions (Spanish)
- Legionnaires’ Disease – Frequently Asked Questions (Vietnamese)
Other Resources
Last Updated: 6/6/2025