Legionnaire's Disease

Original Editor - Itayi Charasika from Bellarmine University's Pathophysiology of Complex Patient Problems project.
Top Contributors - Itayi Charasika, Donald John Auson, Kim Jackson, Kalyani Yajnanarayan, Admin, Elaine Lonnemann, WikiSysop, Adam Vallely Farrell and Nupur Smit Shah

Definition/Description

Legionnaires' Disease is a severe form of pneumonia (lung infection) caused by a bacteria, known as Legionella. It can occur through inhalation of contaminated aerosols such as humidifiers, hot and cold water systems, air conditioning cooling towers and whirlpool spas. Infection can also occur by exposure of babies during water births or aspiration of contaminated ice or water, particularly in susceptible hospital patients. It can be a cause of community acquired pneumonia or hospital acquired pneumonia. This disease is often screened for whenever a person is diagnosed with pneumonia because of the close resemblance Legionnaires' has to pneumonia.

The bacteria, Legionella, in Legionnaires' disease can also cause a milder illness called Pontiac Fever. Pontiac Fever resembles a mild and self-resolving flu-like disease. Unlike Legionnaires' disease, Pontiac Fever usually resolves on its own after 2-5 days.If diagnosed with both illnesses, then the term is Legionellosis.

History of Disease

Legionnaires' disease was first discovered about in 1967 when a group of people in Philadelphia, attending an American Legion convention meeting were exposed to this disease. Those affected suffered from a type of pneumonia, now referred to as Legionnaires’ disease.

The first identified cases of Pontiac fever occurred in 1968 in Pontiac, Michigan, among people who worked at and visited the city’s health department. It wasn’t until Legionella was discovered after the 1976 Legionnaires’ disease outbreak in Philadelphia that public health officials were able to show that Legionella causes both diseases.

                     

Legionnaire's Disease

Etiology

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. 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.

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

Prevalence

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

Facts:

• 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.
• The majority of reported cases are sporadic but 10-20% of them are linked to outbreaks
• 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
• In 2011 California health officials reported Legionnaires disease as a potential diagnosis during a investigation of a mystery illness at the Playboy mansion possibly caused by a fog machine where a 100 people developed respiratory infections. http://www.youtube.com/watch?v=xk5dEOYtPbw&feature=fvsr.

Legionnaire's Disease is found worldwide as illustrated below. 

                                                                  

  

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

Characteristics/Clinical Presentation

Signs & Symptoms:

• Fever
• Dry or productive cough,
• Fatigue
• Anorexia
• Headache
• Myalgia
• Diarrhea
• 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.

                         
What diagnostic tests can confirm Legionnaires' disease?

Diagnostic Tests

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

Test	Advantages	Disadvantages
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

Legionnaires Disease VS Pontiac Fever

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.

Medications

• 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

• 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

Resources

• Legionella(Legionnaire' Disease and Pontiac Fever)- Centers for Disease Control and Prevention
• Legionella.org
• Natural Remedies Encyclopedia
• Legionellosis- WHO