Introduction
Legionella is a pathogenic gram-negative bacteria that includes the species L. pneumophila, which causes legionellosis (all Legionella-caused illnesses), including legionnaires' disease, a pneumonia-like illness, and Pontiac fever, a mild flu-like illness. Legionella was named after a 1976 outbreak of a then-unknown "mystery disease" that sickened 221 people and killed 34. The outbreak was first observed among attendees at an American legion convention - an organization of U.S. military veterans.
What Is Legionella?
Legionella is a gram-negative pathogenic bacteria that causes legionellosis, including legionnaires' disease and Pontiac fever. Legionella bacteria may naturally be found in freshwater lakes and streams. However, bacteria growing and spreading in man-made building water systems can pose a health risk. This includes:
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Showerheads and sink faucets.
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Cooling towers, centralized air cooling systems for buildings or industrial processes.
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Hot tubs.
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Decorative fountains.
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Hot water tanks and heaters.
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Large, complex plumbing systems.
Because air conditioners in homes and cars do not use water to cool the air, they are not at risk for Legionella growth. However, Legionella can grow in a vehicle's windshield wiper fluid tank (such as a car, truck, van, school bus, or taxi), especially if the tank is full of water.
How Do Legionella Infections Spread?
Bacteria thrive in water systems at temperatures ranging from 20 to 50 degrees Celsius (optimal 35 degrees Celsius). Legionella can live and grow as parasites in free-living protozoa and biofilms in water systems. They can cause infections by infecting human cells through a mechanism similar to protozoa infection.
Once Legionella grows and multiplies in a water system, it can spread in small droplets for people to breathe. Legionnaires' disease or Pontiac fever can be contracted by breathing in small droplets of water in the air that contain the bacteria.
People can become ill from aspirating Legionella-contaminated drinking water; however, that is rare. This occurs when water accidentally enters the lungs while drinking. Hence, people with difficulty swallowing are at a higher risk of aspiration. The disease is not contagious; people do not spread legionnaires' disease or Pontiac fever to other people. However, in exceptional circumstances, this may be possible.
Who Are at Risk of Legionella Infections?
Most healthy people who are exposed to Legionella do not become ill. People who are at a higher risk of becoming ill include:
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People aged 50 and older.
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Smokers.
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People suffering from chronic lung disease (like chronic obstructive pulmonary disease or emphysema).
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People with weak immune systems or who use immune-suppressing drugs.
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Cancer patients.
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Individuals suffering from underlying illnesses such as diabetes, kidney failure, or liver failure.
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Advanced age, underlying disease (including prematurity), delayed therapy, and respiratory failure are all risk factors for a poor outcome. However, subsequent episodes are uncommon.
What Are the Symptoms of a Legionella Infection?
People who become ill after exposure to Legionella can develop two diseases known as legionellosis: Legionnaires' disease and Pontiac fever.
Legionnaires' Disease
Legionnaires' disease has symptoms that are similar to other types of pneumonia (lung infection), including:
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Cough.
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Breathing difficulty.
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Fever.
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Muscle pain.
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Loss of appetite.
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Lethargy.
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Headaches
Other symptoms associated with Legionnaires' disease include diarrhea, nausea, and confusion. Symptoms typically appear 2 to 14 days post-exposure to the bacteria, but it can take longer. There is usually a mild cough at first, but phlegm can be present in up to 50 percent of patients. About one-third of patients have blood-streaked phlegm or hemoptysis. The disease's severity ranges from a mild cough to fatal pneumonia. Death occurs due to progressive pneumonia, respiratory failure, shock, and multi-organ failure.
Pontiac Fever
Pontiac fever is a less severe kind of Legionnaires' disease. The most common symptoms are fever and muscle aches. Symptoms usually appear between a few hours and three days after exposure to the bacteria and last less than a week. Pontiac fever differs from Legionnaires' disease because the patient does not have pneumonia.
How Are Legionella Infections Diagnosed?
Legionnaires' Disease
Legionnaires' disease is a severe type of pneumonia (lung infection), which a chest X-ray can confirm. Doctors typically use two types of tests to determine whether Legionella causes a patient's pneumonia:
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Urine examination.
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A laboratory test includes collecting sputum (phlegm) or washing from the lungs.
Pontiac Fever
A urine or blood test can help determine if one has a Pontiac fever. However, a negative test does not rule out the possibility that one may have it (this is called a false negative). Doctors typically diagnose Pontiac fever when lab tests confirm other Legionella infection cases. These confirmed Legionnaires' disease or Pontiac fever patients may have contracted Legionella at the same time or place as other patients with suspected illnesses.
How Are Legionella Infections Treated?
Legionnaires' disease requires antibiotic treatment (using Tetracyclines, Macrolides, and Fluoroquinolones), and most cases are successfully treated. However, the sooner therapy begins, the less likely serious complications could develop. Healthy people usually recover from Legionnaires' disease but typically require hospitalization.
The antibiotics include:
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Fluoroquinolones; the best option is Levofloxacin. Ciprofloxacin and Moxifloxacin are two other drugs.
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Macrolides are antibiotics that include Azithromycin, Clarithromycin, and Erythromycin.
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Doxycycline and other Tetracyclines.
Pontiac fever usually goes away without requiring treatment and does not cause any risks of complications.
What Are the Complications of Legionella Infections?
Legionnaires' disease can cause several potentially fatal complications, including:
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Respiratory Failure: This happens when the lungs cannot provide enough oxygen to the body or remove enough carbon dioxide from the blood.
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Septic Shock: This happens when a sudden, severe drop in blood pressure reduces blood flow to vital organs, particularly the kidneys, and brain. The heart then tries to pump more blood to compensate, but the extra workload eventually weakens the heart and reduces blood flow even more.
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Acute Renal Failure: This is the sudden inability of your kidneys to filter waste from the blood. When the kidneys fail, the body accumulates dangerous levels of fluid and waste.
Legionnaires' disease can cause an individual's death if not treated properly and promptly.
Conclusion
Legionella is a gram-negative pathogenic bacteria that causes legionellosis, including legionnaires' disease and Pontiac fever. It is associated with symptoms such as cough, fever, breathing difficulty, muscle aches, etc. With prompt initiation of appropriate antibiotic therapy, most patients experience symptomatic improvement within 3 to 5 days.
