What are the side effects of Legionnaires' disease?

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Last updated: March 26, 2025View editorial policy

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From the Guidelines

Legionnaires' disease can cause severe side effects, including high fever, pneumonia, and respiratory failure, which can be fatal if left untreated, emphasizing the need for prompt diagnosis and treatment with antibiotics such as azithromycin or a fluoroquinolone 1.

Side Effects of Legionnaires' Disease

The side effects of Legionnaires' disease can vary in severity and include:

  • High fever, often exceeding 104°F
  • Severe pneumonia
  • Cough, which may produce mucus or blood
  • Shortness of breath
  • Chest pain
  • Headaches
  • Muscle aches
  • Fatigue
  • Loss of appetite
  • Gastrointestinal symptoms like nausea, vomiting, and diarrhea
  • Confusion or other neurological symptoms If left untreated, Legionnaires' disease can lead to serious complications, including:
  • Respiratory failure
  • Septic shock
  • Acute kidney injury
  • Death, particularly in vulnerable populations such as the elderly or immunocompromined individuals 1.

Treatment and Prevention

Treatment typically involves antibiotics such as azithromycin (500mg daily for 7-10 days) or levofloxacin (750mg daily for 7-14 days), with hospitalization often necessary for severe cases requiring oxygen therapy or respiratory support 1. The disease is caused by Legionella bacteria, which typically infect the lungs after a person inhales contaminated water droplets from sources like cooling towers, hot tubs, or plumbing systems. Early diagnosis and treatment are crucial to prevent serious complications, and the preferred treatment for legionnaires’ disease for hospitalized patients is azithromycin or a fluoroquinolone (moxifloxacin, gatifloxacin, and levofloxacin; gemifloxacin is only available as an oral formulation) 1.

From the Research

Side Effects of Legionnaires' Disease

The side effects of Legionnaires' disease can be severe and include:

  • Acute kidney injury [ 2, 3,4 ]
  • Rhabdomyolysis [ 2, 3,4 ]
  • Non-occlusive mesenteric ischemia 2
  • Respiratory failure 2, 4
  • Septic shock 2
  • Metabolic acidosis 2
  • Myoglobin cast nephropathy 2
  • Multiple organ failure 2

Treatment-Related Side Effects

Treatment of Legionnaires' disease can also have side effects, including:

  • Adverse effects from erythromycin 5
  • Adverse effects from other antibiotics, although newer macrolides/azalides like clarithromycin and azithromycin have fewer adverse effects 5, 6

Severity of Side Effects

The severity of side effects can vary, with some cases being fatal 2 and others resolving without further complications 3. Early and aggressive management with fluid repletion and appropriate antibiotics can improve clinical manifestations and hospital length of stay 3.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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