Legionnaire's Disease


Legionnaires' Disease is a deadly severe form of pneumonia. It can be a cause of community acquired pneumonia or hospital acquired pneumonia[1]. Legionnaires' disease is a lung infection that can be fatal. It is a disease caused by a bacteria, known as Legionella. This disease is often screened for whenever a person is diagnosed with pneumonia because of the close resemblance Legionnaires' has to pneumonia. Legionnaires' disease is commonly acquired from inhaling the bacteria.
Legionnaire's Disease
The history of Legionnaires' Disease can be viewed below under History of Disease.

The bacteria, Legionella, in Legionnaires' disease can also lead to Pontiac Fever, which is like a milder version of Legionnaires' disease. Pontiac Fever resembles a mild and self-resolving flu-like disease.[2] If a person is diagnosed with both illnesses, then the term is Legionellosis. Unlike Legionnaires' disease, Pontiac Fever usually resolves on its own after 2-5 days.[2]


History of Disease: Legionnaires' disease first came about in 1967 when a group of people in Philadelphia, attending an American Legion convention meeting became exposed to this disease.  View Legionnaire's Disease video below or please visit http://www.youtube.com/watch?v=8oTf2bGCt-Y.  


The pathogen causing Legionnaires' Disease came from the Legionellaceae family of bacteria. Although the family Legionellaceae now contains more than 40 species, L. pneumophila causes over 90% of human infections. L micdadei, the second most frequently isolated species in human infection, evidently has lower virulence for humans than L. pneumophila as it appears to infect only immunocompromised hosts.[3] Water is the major natural reservoir for Legionella, and the pathogen is found in many different natural and artificial aquatic environments such as cooling towers or water systems in buildings, including hospitals.[4]

Common places that allow Legionella transmission:
1. Potable (drinking) water systems
2. Whirlpool spas
3. Cooling towers 

Conditions for Legionella transmission:
1. Heat
2. Stasis
3. Aerosolization


Accurate data reflecting the true incidence of disease are not available because of underutilization of diagnostic testing and under-reporting.[5] It is a common cause of severe pneumonia requiring hospitalization.


  • Responsible for ~ 5% of all pneumonias
  • 12,000 people affected yearly in the U.S
  • Each year an estimated 8,000-18,000 hospitalized cases occur in the U.S.[6]
  • The majority of reported cases are sporadic but 10-20% of them are linked to outbreaks[6]
  • Travel-associated outbreaks, outbreaks in community settings, and nosocomial and occupational outbreaks are common
  • More than 20% of all cases are thought to be associated with recent travel
  • Difficult to detect among travelers because of the low attack rate, long incubation period, and the dispersal of persons  from the source of the outbreak
  • Present rate is that 80% of those contracting the disease die


For recent breaking news on Legionnaire's Disease regarding California health officials investigating a mystery illness at the Playboy mansion possibly caused by a fog machine, please visit http://www.youtube.com/watch?v=xk5dEOYtPbw&feature=fvsr.

♦ Legionnaire's Disease is not only found in the United States, but it is worldwide. ♦

            Image:World_images.jpg                                                      Images3.jpg


Associated Comorbidities

People at risk:

  • Smokers (current and former)
  • Chronic lung disease
  •  Advanced age (50 years and above)
  • Alcohol abuse
  • Surgery
  • Recent travel with an overnight stay outside of the home
  • Exposure to whirlpool spas
  • Recent repairs or maintenance work on domestic plumb
  • Immune system compromised by

          o DM
          o Renal Failure
          o Cancer (esp. hematological or pulmonary malignancy)
          o AIDS

Characteristics/Clinical Presentation

For patient stories on contracting Legionnaires' Disease, visit http://www.youtube.com/watch?v=n5tL69KVTZg.


Many patients report having the following symptoms: Images4.jpg 

S/S: Fevers, chills, dry or productive cough, fatigue, anorexia, headache, myalgia, diarrhea, muscle aches, & gastrointestinal symptoms

Systemic Involvement

Gastrointestinal symptoms include nausea, vomiting, diarrhea, and anorexia.

Neurologic symptoms include headache, lethargy, altered mental status, and rarely, focal symptoms.

Musculoskeletal symptoms include arthralgias and myalgias.

Nonpulmonary symptoms are prominent early in the disease.

Diagnostic Tests/Laboratory Findings:

Legionnaire’s disease is diagnosed by growing bacteria on a special medium and silver staining. The bacteria is identified in the sputum and the Legionella antigen is seen in the urine.

          Images6.jpg                Images8.jpg
What diagnostic tests can confirm Legionnaires' disease?[7]

Diagonostic Tests




Culture - Clinical & Environmental isolates can be compared
- Detects all species & serogroups
- 100% specific
- Technically difficult
- Slow (>5 days to grow)
- Sensitivity highly dependent on technical skill
- May be affected by antibiotic treatment
Urine Antigen - >99% specific...
- Rapid (same day)
- ...but only for L. pneumophila serogroup 1 (Lp1) [ which may account for up to 80% of cases]
- Limited utility when compared to environmental isolates
Serology - Not affected by antibiotic treatment
- 70-80% sensitive; >90% specific
- Must have paired sera
- 5-10% of population has titer 1:≥256
Single acute phase antibody titers of 1:≥256 do not discriminate between cases of Legionnaires' disease and other causes of community-acquired pneumonia.
DFA - Can be performed on pathologic specimens
- 95% specific
- 25-75% sensitive

Medical Management


► Erythromycin (the drug of choice for prolonged period) - given early

► Rifampin is also a benefit

Newer Effective Therapeutic Options Include Antibiotics (Macrolides):
► Clarithromycin

► Azithromycin

► Fluoroquinolones

Patients diagnosed with Legionnaire's Disease are prescribed to take the various medications. 

For patients with Pontiac fever: it is a self-limited illness that does not benefit from antibiotic treatment. Complete recovery usually occurs within 1 week.

Physical Therapy Management

Screening Questions:

    - Have you traveled recently? (Patient could have traveled-associated Legionnaire’s disease[7]

Top 10 Things Every Clinician Needs to Know About Legionellosis

What does the diagnosis of Legionnaire’s disease include? Two clinical syndromes:

Legionnaire's Disease vs. Pontiac Fever
Legionnaires' disease Pontiac fever
Clinical Features Pneumonia: cough, fever, chest pain Flu-like illness (fever, chills, malaise) without pneumonia
Radiographic pneumonia Yes No
Incubation period 2-14 days after exposure 24-48 hours after exposure
Etiologic agent Legionella species Legionella species
Attack rate* < 5% > 90%
Isolation of organism Possible Virtually never
Outcome Hospitalization common
Case-fatality rate: 5-40%**
Hospitalization uncommon
Case-fatality rate: 0%
Additional Below*

  * Percent of persons who, when exposed to the source of an outbreak, become ill.
** Percent of persons who die from Legionnaires' disease or Pontiac fever.

Tests In Relationship to Snout/Spin
Test Sensitivity (%) Specificity (%)
Culture 80 100
Urine antigen 70 100
Paired serology* 70-80 >90
Direct fluorescent antibody stain 25-75% 95
*Note: A single antibody titer of any level is not diagnostic of legionellosis


Patient Care: Respiratory Therapists/PTs: O2 therapy, repositioning, postural drainage, suctioning

Monitor: Chest wall expansion, depth/pattern of ventilations, cough, chest pain, restlessness, & hypoxemia

Signs of Shock: ↓ blood pressure, tachycardia w/weak thread pulse, diaphoresis, clamy skin, & cold

Patient Education: Pulmonary hygiene, deep breathing and coughing exercises, chest physiotherapy, postural drainage, disposal of solid tissues to prevent disease transmission

Differential Diagnosis

  • Adult Respiratory Distress Syndrome (ARDS)
  • Bronchitis
  • Congestive heart failure
  • Gastroenteritis
  • HIV infection and AIDS
  • Inflammation of the rib cartilage (costochondritis)
  • Meningitis
  • Non-Legionnaire's pneumonia
  • Pleural effusion
  • Pneumonia caused by other organisms
  • Prostatitis
  • Septic shock
  • Tuberculosis

Case Reports/ Case Studies

Atypical Presentation of Legionnaire’s Disease: A Case Report and Review
Severe Legionnaires disease complicated by multi-organ dysfunction in a previously healthy patient: a case report
Legionnaires Disease: A Case Study



  1. Pedro-Botet M. L., Sabria-Leal M., Haro M., Rubio C., Gimenez G., Sopena N., Tor J.Nosocomial and community-acquired Legionella pneumonia: clinical comparative analysis. Eur. Respir. J.8199519291933 retrieved from https://erj.ersjournals.com/content/8/11/1929.short
  2. 2.0 2.1 Sharma L, Losier A, Tolbert T, Dela Cruz CS, Marion CR. Atypical Pneumonia: Updates on Legionella, Chlamydophila, and Mycoplasma Pneumonia. Clin Chest Med. 2017;38(1):45–58. doi:10.1016/j.ccm.2016.11.011 retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5679202/
  3. Myerowitz RL, Pasculle AW, Dowling JN et al. (1971) Opportunistic lung infection due to “Pittsburgh Pneumonia Agent”. N Engl J Med 301: 953–958.
  4. Cunha BA, Burillo A, Bouza E, Legionnaires' disease, The Lancet, Volume 387, Issue 10016, 2016, Pages 376-385, ISSN 0140-6736, https://doi.org/10.1016/S0140-6736(15)60078-2 retrieved from https://www.sciencedirect.com/science/article/pii/S0140673615600782
  5. Plouffe JF, Breiman RF, Fields BS, Herbert M, Inverso J, Knirsch C, Kolokathis A, Marrie TJ, Nicolle L, Schwartz DB, Azithromycin in the Treatment of Legionella Pneumonia Requiring Hospitalization, Clinical Infectious Diseases, Volume 37, Issue 11, December 2003, Pages 1475–1480, https://doi.org/10.1086/379329 retrieved from https://academic.oup.com/cid/article/37/11/1475/372119
  6. 6.0 6.1 Legionnaires' Disease available at https://emedicine.medscape.com/article/220163-overview
  7. 7.0 7.1 Legionnaires Disease- CDC available at https://www.cdc.gov/legionella/index.html