Update: Legionnaires' Disease Increase in the Anaheim area
November 8, 2017
The Orange County Health Care Agency has been notified of 11 individuals diagnosed with Legionnaires’ disease who live in or have visited the Anaheim area during the month of September. Eight have a history of visiting Disneyland Parks prior to developing illness; three have no history of Disneyland exposure. Case ages range from 52-94. Ten of the 11 ill were hospitalized, and one person died. OCHCA is currently investigating these cases, but have not yet identified a common exposure for all cases.  

Providers Should
  • Consider Legionnaires’ disease in any patient who develops illness with pneumonia who lives in, works in or has traveled to Anaheim or Disneyland within 10 days of symptom onset

  • Report any suspect or confirmed case of Legionnaires’ 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).  
Background
Legionellosis refers to illness caused by Legionella bacteria and usually results from exposure to contaminated water aerosols or from aspirating contaminated water. Over twenty Legionella species have been implicated in human disease. But Legionella pneumophila is the most common cause of infection, and the majority of L. pneumophila infections are caused by serogroup 1. The annual case report count for Legionnaires’ disease in Orange County over the last five years has ranged from 16-53. Case counts have increased in the County over that time, similar to increased counts seen nationally, and particularly in Southern California. The cause for these increases is unclear.

Legionellosis presents in two distinct illness patterns:
  • Legionnaires’ disease is a 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 particular risk include those who are:
  • Immunocompromised
  • Have chronic lung disease
  • 50 years of age or older
Diagnosis
Legionellosis can be diagnosed by testing for Legionella antigen in the urine of infected patients, and most cases are diagnosed in this fashion. Note that urine antigen testing only identifies L. pneumophila serogroup 1, not other serogroups.  Legionella of all species and serogroups can also be identified by culturing from bronchoalveolar lavage samples. Sputum culture can also be utilized, but is less sensitive than culture of the lower respiratory tract. Special media is necessary to isolate Legionella .
 
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.
Treatment
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:
Contact Information
If you have any questions or concerns please contact the Epidemiology and Assessment Program at (714) 834-8180.
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