The key difference between legionella and legionnaires disease is that legionella disease is a combination of a severe form of lung infection (pneumonia) and a less severe form of flu known as Pontiac fever, while legionnaires disease is a severe form of pneumonia.
Legionella is a genus of pathogenic gram-negative bacteria, which includes pathogenic species such as Legionella pneumophila, Legionella longbeachae, Legionella feeleii, Legionella micdadei, and Legionella anisa. They can cause a mild flu-like illness called Pontiac fever and a pneumonia-type illness called legionnaires disease. Therefore, legionella and legionnaires disease are two types of illnesses caused by the pathogenic bacteria belonging to the genus Legionella.
CONTENTS
1. Overview and Key Difference
2. What is Legionella Disease
3. What is Legionnaires Disease
4. Similarities – Legionella and Legionnaires Disease
5. Legionella vs Legionnaires Disease in Tabular Form
6. Summary – Legionella vs Legionnaires Disease
What is Legionella Disease?
Legionella Disease (legionellosis) varies in severity from a mild febrile illness to a severe, fatal form of pneumonia. It is caused by exposure to Legionella bacteria species normally found in contaminated water and potting mixes. The cases of legionella disease are often categorized under community, travel, or hospital-acquired infections. Throughout the world, waterborne Legionella pneumophila is the most common cause of the cases, also including outbreaks. The most common form of transmission of this Legionella species is the inhalation of contaminated aerosols from contaminated water. The other species that cause mild febrile illness (Pontiac fever) include Legionella longbeachae, Legionella feeleii, Legionella micdadei, and Legionella anisa. These species are spread by breathing in water droplets in the air at home, at work, in hospitals, or other public places.
Figure 01: Legionella Disease
The symptoms of the non-pneumonic form include acute, self-limiting influenza-like illnesses characterized by fever, chills, headache, malaise, and myalgia. Symptoms of the pneumonic form include fever, loss of appetite, headache, malaise, lethargy, diarrhea, confusion, cough, blood-streaked phlegm, and shock. The risk factors include age over 50 years, smoking, chronic lung disease, immune system disorder due to disease or medication, systematic malignancy, underline illness such as diabetes, renal failure, hepatic failure, recent travel with an overnight stay outside of the home, recent care at a health care facility, and exposure to hot tubs. Legionella disease can be diagnosed through medical history, physical examination, blood test, urine test, sputum test, chest X-ray, serology test (direct fluorescent antibody (DFA), and PCR. Furthermore, legionella disease can be treated through antibiotics, anti-pyretic drugs, and taking rest.
What is Legionnaires Disease?
Legionnaires disease is a severe form of lung infection called pneumonia. It is commonly caused by Legionella pneumophila. Most people catch this illness by inhaling the above Legionella species in water (hot baths, cooling towers, hot water tanks, decorative fountains, swimming pools, birthing pools, drinking water) or soil. The typical symptoms of this condition may include headache, muscle aches, fever, cough, shortness of breath, chest pain, nausea, vomiting diarrhea, confusion, mental changes, shock, kidney problems, and heart problems. Moreover, older adults, smokers, and people with weakened immunity are particularly susceptible to legionnaires disease.
Figure 02: Legionnaires Disease
Legionnaires disease can be diagnosed through physical examination, blood test, urine test, chest X-ray, and test on a sample of sputum or lung tissue. Furthermore, treatment options for legionnaires disease include antibiotics such as fluoroquinolones (levofloxacin and moxifloxacin) and macrolides like azithromycin and clarithromycin.
What are the Similarities Between Legionella and Legionnaires Disease?
- Legionella and legionnaires disease are two types of illnesses caused by the pathogenic bacteria belonging to the genus Legionella.
- The causative agents of both diseases are gram-negative pathogenic bacteria, and they are transmitted mainly through contaminated water.
- The causative agents of both diseases do not transmit from person to person.
- Both diseases can be diagnosed through blood and urine tests.
- They are treated through medications like antibiotics.
What is the Difference Between Legionella and Legionnaires Disease?
Legionella disease is a combination of a severe form of lung infection (pneumonia) and a less severe form of flu called Pontiac fever, while legionnaires disease is only a severe form of pneumonia. Thus, this is the key difference between legionella and legionnaires disease. Furthermore, legionella disease is mainly caused by Legionella pneumophila, Legionella longbeachae, Legionella feeleii, Legionella micdadei, or Legionella anisa. On the other hand, legionnaires disease is mainly caused by Legionella pneumophila.
The below infographic presents the differences between legionella and legionnaires disease in tabular form for side-by-side comparison.
Summary – Legionella vs Legionnaires Disease
Legionella and legionnaires disease are two types of illnesses caused by the gram-negative pathogenic bacterial species belonging to the genus Legionella. These Legionella species are normally found in a variety of artificial water systems, natural fresh waters, and soils. Legionella disease is a combination of a severe form of lung infection (pneumonia) and a less severe form of flu known as Pontiac fever, while legionnaires disease is only a severe form of pneumonia. So, this is the key difference between legionella and legionnaires disease.
Reference:
1. “Legionellosis (Legionella): Legionnaires Disease and Pontiac Fever.” Minnesota Dept. of Health.
2. “Legionnaires’ Disease.” Mayo Clinic, Mayo Foundation for Medical Education and Research.
Image Courtesy:
1. “Lung tissue during legionellosis” (CC0) via Picryl
2. “Legionella pneumonia” By Atlas of Pulmonary Pathology (CC BY-SA 2.0) via Flickr