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Legionnaires' Disease

Severe pneumonia caused by Legionella species

Written by: Saygı Hospital Health Guide Editorial Board
Published:

This content is for general information; please consult your physician for diagnosis and treatment.

This content is for informational purposes only and does not constitute medical advice. You can book an appointment at our Göğüs Hastalıkları department. Book Appointment →

What is Legionnaires' Disease?

Legionella are aerobic, gram-negative intracellular bacilli that survive in water and amoebae. L. pneumophila serogroup 1 causes ~80% of cases; L. longbeachae (potting soil exposure) and other species also cause disease.

Transmission occurs via inhalation or aspiration of aerosolized water from cooling towers, hot water systems, whirlpool spas, decorative fountains, humidifiers, nebulizers, and building plumbing. Not transmitted person-to-person.

Incubation 2–14 days. Organism replicates within alveolar macrophages causing multifocal pneumonia with lobular, lobar, or cavitary patterns; extrapulmonary involvement (hepatitis, hyponatremia, neurologic, renal) is characteristic.

Clinical forms: Legionnaires' pneumonia (severe) and Pontiac fever (mild self-limited influenza-like illness without pneumonia). Diagnosis by urinary antigen (L. pneumophila serogroup 1), respiratory culture, PCR, or paired serology.

Symptoms

Abrupt onset of high fever (often >39°C), chills, malaise
Dry cough progressing to productive, dyspnea, chest pain
Gastrointestinal symptoms: nausea, vomiting, watery diarrhea, abdominal pain
Neurologic: confusion, headache, encephalopathy
Relative bradycardia (temperature-pulse dissociation), hyponatremia
Severe: respiratory failure, septic shock, acute kidney injury, multiorgan dysfunction

Risk Factors

Age ≥50 years, especially with underlying chronic disease
Smoking — current or recent; COPD, emphysema
Diabetes mellitus, chronic kidney disease, chronic heart or liver disease
Immunosuppression: organ transplant, chemotherapy, TNF-α antagonists, corticosteroids
Recent travel with stay in hotels, cruise ships, hospitals, long-term care facilities
Exposure to cooling towers, whirlpool spas, decorative water features, aerosol-generating medical devices

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • Severe community-acquired pneumonia with atypical features (high fever, neurologic/GI symptoms, hyponatremia, LFT abnormalities), travel/exposure history, or outbreak setting warrants urgent evaluation and empirical legionella coverage per IDSA/ATS.
  • Respiratory failure, septic shock, altered mental status, or multiorgan dysfunction require emergency admission, ICU evaluation, and aggressive antimicrobial and supportive therapy.
  • Clusters of pneumonia linked to a common location (hotel, hospital, building with cooling tower) require public health notification and environmental investigation for source control.

Treatment Methods

01
First-line: respiratory fluoroquinolone (levofloxacin 750 mg daily, moxifloxacin 400 mg daily) or azithromycin 500 mg daily × 7–10 days for immunocompetent; 14–21 days for severe or immunocompromised.
02
Severe disease or ICU admission: IV levofloxacin or combination with azithromycin; de-escalate to oral when improving.
03
Supportive: oxygen, mechanical ventilation if respiratory failure, fluid resuscitation, vasopressors for septic shock, correction of hyponatremia; ICU-level monitoring.
04
Investigate for underlying environmental source — urinary antigen testing on other cases, water system assessment; collaborate with public health and infection control.
05
No specific immunization available; emphasize prevention through water management.
06
Prevention: water safety plans per WHO/ASHRAE — temperature control (>60°C hot water, <20°C cold), chlorination, cleaning of cooling towers and spas, point-of-use filters in high-risk units; monitor high-risk buildings routinely.

Which Department to Visit?

You can visit our Göğüs Hastalıkları department for these complaints. Our specialist physicians will create the most suitable treatment plan for you.

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Health Disclaimer: The information on this page is prepared for general informational purposes only. It does not replace medical diagnosis and treatment. Please consult your physician for your complaints. Saygı Hospital does not accept responsibility for actions taken based on the information on this page.