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Published on: 7/21/2026

What is the mortality rate for Legionnaires' disease?

Yoshinori Abe

Reviewed by Yoshinori Abe, MD

Internal Medicine

Legionnaires' disease has a mortality rate of approximately 10%, though this can rise to 25% or higher in severe cases, hospital-acquired infections, or when treatment is delayed. Key factors influencing survival include age, underlying health conditions (such as weakened immunity, chronic lung disease, or diabetes), and how quickly antibiotic therapy begins. Early diagnosis dramatically improves outcomes, making prompt recognition of symptoms — like high fever, cough, shortness of breath, muscle aches, and confusion — critically important.

Because Legionnaires' disease can escalate rapidly and mimic other respiratory illnesses, waiting to see if symptoms improve on their own can be risky. If you or a loved one are experiencing concerning symptoms, taking a few minutes to complete a free, instant, online symptom check can help you better understand what may be going on and guide your next steps — whether that's seeking urgent care or discussing findings with your doctor. Early action saves lives.

Reviewed for medical accuracy: 07/20/2026

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Important Next Steps

Learn if Legionnaires' disease could explain symptomsDiscover how serious your symptoms might beFind out if you need care todaySee OTC options for fever and coughFind a doctor for lung infectionsDiscover safe home remedies for recoveryUnderstand likely causes of pneumonia symptoms

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Explanation

Legionnaires' disease is a type of pneumonia caused by the Legionella bacteria. The mortality rate can be influenced by several factors, including the severity of the illness and how quickly treatment begins.

  • Severe Cases: In severe cases of Legionella pneumonia, the mortality rate is higher. This is especially true for people with weakened immune systems or other health issues.
  • Prompt Treatment: Early diagnosis and treatment with antibiotics can significantly reduce the risk of death.

It is important to seek medical care if symptoms of pneumonia, such as cough, fever, and difficulty breathing, are present. If you're experiencing these symptoms, you can use Ubie's free AI symptom checker to help assess your condition before contacting a healthcare provider. Early intervention can improve outcomes and reduce the risk of severe complications.

(References)

  • el-Ebiary M, Sarmiento X, Torres A, Nogué S, Mesalles E, Bodí M, & Almirall J. (1997). Prognostic factors of severe Legionella pneumonia .... American journal of respiratory and critical care medicine, 9372662.

  • Tran OC, Lucero DE, Balter S, Fitzhenry R, Huynh M, Varma JK, & Vora NM. (2018). Sensitivity and Positive Predictive Value of Death .... Public health reports (Washington, D.C. : 1974), 30005174.

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