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Alert Date: 
Thursday, October 18, 2018 - 12:00pm
Windsor and Essex County

Clinicians Update

The Windsor-Essex County Health Unit is following up on several recent confirmed cases of legionellosis in the Windsor/Essex area. Legionella are bacteria that live in water and can cause Legionnaires’ disease. Legionnaires’ disease is a sometimes-fatal form of pneumonia that is often under recognized and underdiagnosed and occurs more often in the summer and early fall. We would like to take this opportunity to provide a brief update in order for clinicians to consider Legionnaires disease as a differential diagnosis for clients that may present with compatible symptoms.


Detection of legionella is a mandatory reportable disease, according to Health Protection and Promotion Act, R.S.O., 1990. All clinically diagnosed, probable and confirmed cases must be reported to the Health Unit by the next working day.

Signs & Symptoms:

  • Cough, fever and radiographic pneumonia.
  • Anorexia, malaise, myalgia, headache, confusion, chills, nausea, diarrhea
  • Similar to pneumonia caused by other pathogens.
  • The only way to tell if a patient with pneumonia has Legionnaire’s disease is with specific diagnostic testing.

Diagnosis, Testing and Management:


Indications that warrant testing for Legionella include:

  • Patients with severe pneumonia, especially those that require intensive care
  • Immunocompromised patients with pneumonia
  • Patients who have failed outpatient antibiotic therapy for community-acquired pneumonia
  • Patients with hyponatremia, elevated hepatic transaminase, or C-reactive protein levels>100mg/L.
  • Patients with a travel history (have traveled away from their home within 10 days of illness onset)
  • Patients with other risk factors

Risk Factors:

  • Age > 50 years
  • Smoking (current or historical)
  • Chronic lung disease (i.e. emphysema or COPD)
  • Immune system disorders due to disease or medication
  • Systemic malignancy
  • Underlying illness, such as diabetes, renal or hepatic failure


  • Urinary antigen testing is the most rapid and sensitive test, however only detects Legionella pneumophila serogroup 1
  • Cases with positive urine antigen are recommend to have confirmatory lower respiratory secretion cultures.
  • Isolation of Legionella by culture is important for detection of other species and subgroups for public health investigation
  • Best practice is to obtain both sputum culture and a urinary antigen test concurrently.
    Public Health Ontario Laboratory is available for consultation on laboratory testing with health care providers as needed at (toll free) 1-877-604-4567 or accessed through the links below:




    • Macrolides and respiratory fluoroquinolones are currently the preferred agents for treating Legionnaires disease.


    While Legionella is found in natural, freshwater environments, it can become a health concern in human-made water systems (i.e., plumbing system of large buildings, cooling towers, certain medical devices, decorative fountains and hot tubs) where conditions allows it to multiply and come in contact with vulnerable populations.

    People contract Legionella by inhaling aerosolized water droplets containing the bacteria, or, less commonly, by aspiration of contaminated drinking water. Legionella is not transmitted from person to person. Fortunately, most people exposed to the bacteria do not become ill.

    Our website ( is a reference for health care providers and patients. For additional information or consultation, please call the Health Unit during regular office hours at 519-258-246 ext. 1420. During after hours and weekends, please call 519-973-4510.

    Dr. Wajid Ahmed, MBBS, MAS, MSc, FRCPC
    Medical Officer of Health

    For more information