Legionnaires’ Disease

Legionellosis, also known as Legionnaires’ disease (LD), is a potentially fatal infectious disease caused by the thin, gram-negative, pleomorphic, flagellated, non-sporing forming, aerobic bacteria belonging to the genus Legionella. Over 90% of legionellosis cases are caused by Legionella pneumophila, a ubiquitous aquatic organism that thrives in temperatures between 25 and 45°C (77 and 113°F), with an optimum around 35°C (95°F).

legionnaires disease,lung infection,legionella pneumonia,pontiac fever,pulmonary infection,legionella pneumophila

Legionella Temperature Chart

Legionellosis takes two distinct forms:

  • Legionnaires’ disease, also known as “Legion Fever”, is the more severe form of the infection and
    produces pneumonia.
  • Pontiac Fever is a milder infection, also caused by Legionella spp with symptoms similar to those of Legionnaires’ disease and usually last for 2-5 days. Pontiac fever is different from Legionnaires’ disease because the patient does not have pneumonia and the symptoms go away on their own without treatment.

Legionnaires’ disease acquired its name in July 1976 when an outbreak of pneumonia occurred among people attending a convention of the American Legion at the Bellevue-Stratford Hotel in Philadelphia. On January 18, 1977 the causative agent was identified as a previously unknown bacterium, subsequently named Legionella pneumophila and the name of the illness was changed to Legionellosis.

Outbreaks of Legionnaires’ disease receive significant media attention. However, this disease usually occurs as single, isolated cases not associated with any recognized outbreak. When outbreaks do occur, they are usually in the summer and early autumn, though cases may occur at any time of year. The fatality rate of Legionnaires’ disease has ranged from 5% to 30% during various outbreaks. “The death rate for patients who develop Legionnaire’s disease while in the hospital is close to 50%, especially when antibiotics are started late”, according to the NIH and U.S. National Library of Medicine service’s MedlinePlus. Most infections occur in those who are middle-age or older.

Chart on Legionella Outbreaks by System Types

Chart on Legionella Outbreaks by System Types

Legionnaires’ Disease Ranks Fourth Among Causes of Pneumonia (Lung Infection)

Legionella bacteria grow and thrive in the lungs. The bacteria enter through the alveoli. People get Legionnaires’ disease when they breathe in a mist or vapor (small droplets of water in the air) containing the bacteria.

Legionnaires' Disease affects the lungsLegionnaires' Disease as seen in the lungs

Lung Infection from Legionnaires Disease

Every year between 8,000 – 20,000 people are sent to the hospital in the U.S. Many infections are not reported or diagnosed so this number might be higher or lower. Most outbreaks and infections are in the Summer and early Fall and have similar symptoms to the swine flu.

What Are The Symptoms?

The symptoms of Legionnaires’ Disease, or Legionellosis, are most similar to those of pneumonia, so it can be difficult to diagnose early on. They will normally develop within 2 – 14 days after contact with the bacteria and symptoms include:

  • headache
  • muscle pain
  • chills and/or fever
  • shortness of breath and/or chest pain
  • fatigue
  • cough
  • loss of appetite
  • nausea, vomiting and diarrhea
  • confusion or other mental changes

Legionella pneumophila most often causes pneumonia with extrapulmonary features. Chest X-rays are often used to locate the pneumonia, and other tests can be done on sputum or phlegm, as well as blood and urine tests can be used to determine evidence of the bacteria in the body.

A milder variation of the infection is known as Pontiac Fever. The symptoms of Pontiac Fever usually last for 2 to 5 days and may also include fever, headaches, and muscle aches. These symptoms typically go away on their own without treatment and without causing further problems. Because the two diseases are so similar, it can be difficult to determine which of the two you could be suffering from.

Risk Factors for Legionnaires’ Disease (Legionellosis)

  • Recent travel with an overnight stay outside the home
  • Exposure to whirlpool spas
  • Recent repairs or maintenance work on domestic plumbing
  • Renal, hepatic failure, chronic respiratory or kidney disease
  • Diabetics, cancer sufferers
  • Systemic malignancy
  • Current or former smokers and alcoholics
  • Immune system disorders
  • Age over 50
  • Gender: men

How Legionnaires’ Disease is Spread

Legionnaires’ disease cannot be spread from person to person. People get Legionnaires’ disease when they breathe in a mist or vapor (small droplets of water in the air) containing the bacteria.

Outbreaks occur when two or more people contract the bacteria in the same place at about the same time. The spread of Legionellosis is actually people becoming infected from the same infected water source, within a similar time frame.

These outbreaks most often occur in hospitals, healthcare centers, and continuous care retirement centers (CCRC). These buildings have complex water systems, and many patients and employees in these types of buildings or facilities, are already subject to illnesses that increase their risk for Legionella infection.

Other environments conducive to outbreaks have been linked to aerosol sources in the community, or on cruise ships and in hotels.

Legionnaires’ Disease occurs when people breathe mists from water sources contaminated with Legionella bacteria. The disease is normally contracted by inhaling Legionella bacteria deep into the lungs. Legionella species can be found in tiny droplets of water (aerosols) or in droplet nuclei (the particles left after the water has evaporated).

How is Legionnaires's Disease Spread?

How is Legionnaires’s Disease Spread?

Aerosol-generating devices such as wet cooling towers and water systems are well documented as sources of Legionnaires’ disease. Spas have also been widely acknowledged as a source of exposure in outbreaks.

Every year in the U.S., there are an estimated 25,000 cases of Legionnaires’s disease and 4,000 deaths.

On average in America, 11 people die every day from Legionnaires’s disease. Another 57 people are infected. For those who
recover from the acute illness, severe infections may cause long-term debilitating effects in brain function, kidney function and respiratory capacity. There are nearly as many deaths in America each year from Legionnaires’s disease as there are deaths from workplace accidents.

How Do I Get Treated?

The goal of treatment for Legionnaires’ disease is to eliminate the infection with antibiotics. Treatment is started as soon as Legionnaire’s disease is suspected, without waiting for confirmation by culture results.

Most cases of Legionella pneumonia show improvement within 12-48 hours of starting antibiotic therapy. The antibiotic of choice has been erythromycin, sometimes paired with a second antibiotic, rifampin. Tetracycline, alone or with rifampin, is also used to treat Legionnaires’ disease, but has had more mixed success in comparison to erythromycin.

Other antibiotics that have been used successfully to combat Legionella include doxycycline, clarithromycin, fluorinated quinolones, and trimethoprim/sulfamethoxazole.

The type of antibiotic prescribed by the doctor depends on several factors including the severity of infection, potential allergies, and interaction with previously prescribed drugs. For example, erythromycin interacts with warfarin, a blood thinner. Supportive treatment includes hospitalization for fluid and electrolyte replacement and oxygen administration by mask or by mechanical ventilation, if the respiratory system becomes severely compromised by the infection.

Chart of Incident of Legionairies Disease by Age

Incident of Legionnaires Disease by Age

What Precautions Can I Take?

Legionnaires’ is considered an environmental disease because its causative agent (legionellae) is transmitted from an environmental source (water) to a person (in contrast with communicable diseases, such as AIDS, which are transmitted from person to person).

Therefore, keeping legionellae out of water is the key to preventing the disease. For example, plumbing systems can be maintained to minimize the growth of legionellae. And if preventive measures alone do not control the bacteria, disinfection procedures can be implemented.

Building and Facility Water Systems Owners Should:

Legionella Articles Downloads (PDF):

Article on Facilitating supplemental disinfection for legionella control in plumbing systems - 201408Article - Reducing Legionella Infection in Hospitals - 201308ASHRAE Guideline 12-2000 - Minimizing the Risk of Legionellosis Associated with Building Water Systems (PDF)Chlorine Eating Away Pipes at VA - 20150506 - Pittsburgh Tribune Article (PDF)



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