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What Is The Incubation Period For Legionnaires Disease?

Legionnaires’ disease a specific type of Legionellosis health problem refers to a bacterial disease caused by the bacteria called Legionella. Legionnaires’ disease results in severe form of pneumonia requiring immediate hospitalization. Moreover, in some of the cases, the bacteria Legionella causes a few extra-pulmonary infections, which include wound infections or endocarditis.

What is The Incubation Period for Legionnaires Disease?

Doctors say that incubation period with legionnaires’ disease and a patient’s recovery may range from only 2 days period to 10 days.

Legionnaires’ disease often takes place because of the transfer of Legionella bacteria often from the inhalation of polluted aerosols produced in combination with mists, jets and water sprays. This type of infection also takes place due to aspiration of ice or water in polluted form, especially in susceptible patients admitted in the hospital. Even the disease may take place from artificial water systems, as they provide favorable environment for the growth as well as dissemination of the respective bacteria to represent the most common source of the disease.

Legionella bacteria grow and live in water systems at temperature ranging between 20 degrees to 50 degrees Celsius with optimal temperature of 35 degree Celsius. Even the bacterium may grow as parasite in any free-living type of protozoa developing in the water systems. These cause infections in human cells by applying almost same mechanism, as that applied by infected protozoa. Furthermore, you will find a few common risk factors related to travel-related or community-acquired type of Legionnaires’ disease, which includes heavy drinking and smoking, immune-suppression, pulmonary disease, renal or chronic respiratory problems.

Detailed Study on Incubation Period And Death Rate of Legionnaires’ Disease

As a form of pneumonia, the Legionnaires’ disease incorporates an incubation period from minimum 2 days to maximum 10 days, while it has a record of maximum 16 days in some of the outbreaks. Key aspects in this case are-

  • Disease initially starts with fever, headache, appetite loss, lethargy and malaise, along with other pneumonia-related symptoms.
  • A few patients even suffer from confusion, diarrhea, muscular/joint pain, mild cough and cold as well as 50% patients may suffer from phlegm.
  • Moreover, hemoptysis or blood-streaked form of phlegm takes place in approximately one-third of total patients.
  • The disease severity starts from cough and cold to a rapid form of fatal pneumonia.

Among the total reported cases related to the disease, approximately 75% to 80% are more than 50 years age; while among 60% to 70% suffered patients are males. Death from Legionnaires’ disease mainly takes place from progressive form of pneumonia combined with failure of multiple organs or failure of respiratory systems.

When The Problem Remains in Untreated Condition

Health condition of individuals with untreated Legionnaires’ disease often becomes worse during the initial weeks.

Along with common risk factors causing the mentioned severe form of pneumonia, Legionnaires’ disease has a few frequent complications. These include acute and shock kidney failure and failure of other body organs, respiratory system failure and so on.

Recovery in this case always involves application of antibiotic treatment and it completes after several months or weeks.

Death Rate of The Disease

Death rate associated with Legionnaires’ disease depends primarily on its severity, accuracy of initial antibiotic or anti-microbial form of treatment, the exact setting of the acquiring of Legionella and varieties of host factors, including severity as per immune suppression. Death rate in case of untreated immune-suppressed type of patients may range between 40% and 80%, while between 5% and 30% for patients undergoing with appropriate case management. Along with this, death rate depends on clinical symptoms. Overall, death rate in case of Legionnaires’ disease ranges between 5% and 10%.


  1. Centers for Disease Control and Prevention (CDC) – Legionnaires’ Disease: https://www.cdc.gov/legionella/about/index.html
  2. American Lung Association – Legionnaires’ Disease: https://www.lung.org/lung-health-diseases/lung-disease-lookup/legionnaires-disease
  3. Mayo Clinic – Legionnaires’ Disease: https://www.mayoclinic.org/diseases-conditions/legionnaires-disease/symptoms-causes/syc-20351747
  4. European Centre for Disease Prevention and Control (ECDC) – Legionnaires’ Disease: https://www.ecdc.europa.eu/en/legionnaires-disease

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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 3, 2023

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