Legionnaire's Disease

By: Amanda Fisher & Bryan Shurtz. 4-6-16

Cause of Legionnaire's

Legionnaire's Disease is a severe infection caused by Legionellae species, primarily L. Pneumophila.

People At Risk

Most healthy people do not typically become infected with this disease, although some of those infected include:

  • Older people (50 years and older)
  • Current and former smokers
  • People with chronic lung diseases such as COPD or Emphysema
  • People with a weak immune system from diseases like cancer, diabetes, or kidney failure
  • People on drugs that suppress the immune system.


Legionella species are obligate or facultative intracellular parasites that mainly infect and replicate with in protozoa such as Acanthamoeba and Hartmannella which are found in natural and manufactured water systems. This bacteria infected human macrophages and monocytes. The replication of this bacteria is then observed in the aveoli. T cells produce lymphokines that stimulate increased antimicrobial activity in macrophages. This is key in halting the intracellular growth of Legionellae.

Manifestations (Signs & Symptoms)

  1. Symptoms include an incubation period of 2-10 days.
  2. Patients may feel tired and weak
  3. Often a high fever of 103 degrees Fahrenheit
  4. They will have a cough and may cough up sputum
  5. GI symptoms such as diarrhea, nausea, and vomitting
  6. Patients may also experience headaches, muscle aches, and shortness of breath


Complications of Legionnaire's disease includes:

  • Respiratory failure
  • Acute kidney injury
  • Severe sepsis


Antibiotics are the main form of treatment. The two main antibiotics used are:

  • Macrolides ( azithromycin)
  • Quinolones ( ciprofloxacin)
Other medications used include; tetracycline, doxycycline, minocycline, and trimethoprim/ sulfamethoxazole