Legionnaire's Disease in Garden Grove
January 9, 2019
The Orange County Health Care Agency (OCHCA) has recently identified four cases of Legionnaire’s disease in residents of Garden Grove. The first case had an illness onset date of December 21, 2018. OCHCA is currently investigating the cases; a common exposure has not been identified.  
Providers Should
  • Consider Legionnaire’s disease in any patient who develops illness with pneumonia who lives in, works in or has traveled to Garden Grove within 10 days of symptom onset.
  • Report any suspect or confirmed case of Legionnaire’s disease immediately to Orange County Public Health at 714-834-8180 (after hours call 714-628-7008 to speak to the Health Officer on call).  
Legionellosis is caused by Legionella spp . bacteria and usually results from inhalation of aerosolized water containing the bacteria. Over twenty Legionella species have been implicated in human disease.  Legionella pneumophila is the most commonly detected cause of infection in the United States, and the majority of L. pneumophila infections are caused by serogroup 1. Case counts have generally increased in Orange County in recent years (see graph), similar to increased counts seen throughout Southern California. The reason for these increases is unclear.
Legionellosis has two distinct illness presentations:
  • Legionnaires’ disease presents as progressive pneumonia with a 2-10 day incubation period. The disease can also cause cardiac, renal and gastrointestinal involvement.
  • Pontiac fever is a self-limited, influenza-like illness without pneumonia that has a 1-2 day incubation period caused by an inflammatory response to L. pneumophila-produced endotoxin.

Patients at increased risk include those who are:
  • Aged 50 years or older;
  • Smokers;
  • Immunocompromised;
  • Have chronic heart, lung, or renal disease, or diabetes
Legionnaire’s disease can be diagnosed by testing for Legionella antigen in the urine of infected patients and most cases are diagnosed using this method. However, urine antigen testing only identifies L. pneumophila serogroup 1. All Legionella species and serogroups can be identified by culture of sputum or bronchoalveolar lavage specimens, but culture is less sensitive in patients who have already begun antibiotic therapy.
Testing for legionellosis should be considered particularly in patients who have failed outpatient antibiotic therapy for community-acquired pneumonia and patients with severe pneumonia, such as those requiring intensive care.

Azithromycin or levofloxacin can be utilized to treat Legionnaires’ disease. Levofloxacin (or another fluoroquinolone) is the drug of choice for immunocompromised adults. 
Environmental Sources of Legionella
Legionella species are naturally occurring, ubiquitous aquatic organisms. Hot tubs are a common source of Legionella ; proper hot tub maintenance is vital in preventing potential exposure. Other common sources include household showers, decorative fountains and cooling towers (parts of centralized air-conditioning systems for large buildings). Healthcare-associated legionellosis cases can occur and are related to contamination of the facility’s hot water supply. Any healthcare associated infection requires assessment for potential ongoing risk.
Additional Information
For additional information on diagnosis, treatment, or prevention of Legionellosis: https://www.cdc.gov/legionella/downloads/fs-legionella-clinicians.pdf
For additional information on water system maintenance:
For questions or concerns please contact the Epidemiology and Assessment Program at 714-834-8180.
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