Legionnaires' Disease
Disease Details
Family Health Simplified
- Description
- Legionnaires' disease is a severe form of pneumonia caused by the bacterium Legionella pneumophila, often contracted by inhaling contaminated water droplets.
- Type
- Legionnaires' disease is a type of bacterial infection caused by Legionella pneumophila. It is not genetically transmitted; rather, it is typically acquired through inhalation of aerosolized water or soil contaminated with the bacteria.
- Signs And Symptoms
- The length of time between exposure to the bacteria and the appearance of symptoms (incubation period) is generally 2–10 days, but can more rarely extend to as long as 20 days. For the general population, among those exposed, between 0.1 and 5.0% develop the disease, while among those in hospital, between 0.4 and 14% develop the disease.Those with Legionnaires' disease usually have fever, chills, and a cough, which may be dry or may produce sputum. Almost all experience fever, while around half have cough with sputum, and one-third cough up blood or bloody sputum. Some also have muscle aches, headache, tiredness, loss of appetite, loss of coordination (ataxia), chest pain, or diarrhea and vomiting. Up to half of those with Legionnaires' disease have gastrointestinal symptoms, and almost half have neurological symptoms, including confusion and impaired cognition. "Relative bradycardia" may also be present, which is low to normal heart rate despite the presence of a fever.Laboratory tests may show that kidney functions, liver functions, and electrolyte levels are abnormal, which may include low sodium in the blood. Chest X-rays often show pneumonia with consolidation in the bottom portion of both lungs. Distinguishing Legionnaires' disease from other types of pneumonia by symptoms or radiologic findings alone is difficult; other tests are required for definitive diagnosis.People with Pontiac fever, a much milder illness caused by the same bacterium, experience fever and muscle aches without pneumonia. They generally recover in 2–5 days without treatment. For Pontiac fever, the time between exposure and symptoms is generally a few hours to two days.
- Prognosis
- The fatality rate of Legionnaires' disease has ranged from 5–30% during various outbreaks and approaches 50% for nosocomial infections, especially when treatment with antibiotics is delayed. Hospital-acquired Legionella pneumonia has a fatality rate of 28%, and the principal source of infection in such cases is the drinking-water distribution system.
- Onset
- Legionnaires' disease typically presents with symptoms 2 to 10 days after exposure to Legionella bacteria. The onset usually begins with flu-like symptoms such as fever, chills, headache, and muscle aches, followed by severe pneumonia.
- Prevalence
- Legionnaires' disease is relatively uncommon, with the prevalence varying by region. In the United States, the Centers for Disease Control and Prevention (CDC) reports approximately 8,000 to 18,000 cases annually, though it is likely underreported. Outbreaks can occur in various settings, particularly those involving complex water systems.
- Epidemiology
- 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. Of the 182 reported cases, mostly men, 29 died. On 18 January 1977, the causative agent was identified as a previously unknown strain of bacteria, subsequently named Legionella, and the species that caused the outbreak was named Legionella pneumophila. Following this discovery, unexplained outbreaks of severe respiratory disease from the 1950s were retrospectively attributed to Legionella. Legionnaires' disease also became a prominent historical example of an emerging infectious disease.Outbreaks of Legionnaires' disease receive significant media attention, but this disease usually occurs in 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. Most infections occur in those who are middle-aged or older. National surveillance systems and research studies were established early, and in recent years, improved ascertainment and changes in clinical methods of diagnosis have contributed to an upsurge in reported cases in many countries. Environmental studies continue to identify novel sources of infection, leading to regular revisions of guidelines and regulations. About 8,000 to 18,000 cases of Legionnaires' disease occur each year in the United States, according to the Bureau of Communicable Disease Control.Between 1995 and 2005, over 32,000 cases of Legionnaires' disease and more than 600 outbreaks were reported to the European Working Group for Legionella Infections. The data on Legionella are limited in developing countries, and Legionella-related illnesses likely are underdiagnosed worldwide. Improvements in diagnosis and surveillance in developing countries would be expected to reveal far higher levels of morbidity and mortality than are currently recognised. Similarly, improved diagnosis of human illness related to Legionella species and serogroups other than Legionella pneumophila would improve knowledge about their incidence and spread.A 2011 study successfully used modeling to predict the likely number of cases during Legionnaires' outbreaks based on symptom onset dates from past outbreaks. In this way, the eventual likely size of an outbreak can be predicted, enabling efficient and effective use of public-health resources in managing an outbreak.During the COVID-19 pandemic, some researchers and organisations raised concerns about the impact of the COVID-19 lockdowns on Legionnaire's disease outbreaks. Additionally, at least two people in England died from a co-infection of Legionella and SARS-CoV-2.
- Intractability
- Legionnaires' disease is not considered intractable when promptly diagnosed and appropriately treated. It is a severe form of pneumonia caused by Legionella bacteria, typically treated with antibiotics such as macrolides or fluoroquinolones. However, if left untreated, it can lead to serious complications or be fatal, particularly in vulnerable populations such as the elderly, smokers, or those with weakened immune systems.
- Disease Severity
- Legionnaires' disease can vary in severity. It often results in severe pneumonia and can be life-threatening, especially for older adults, smokers, and individuals with weakened immune systems. The illness requires prompt medical treatment and can lead to complications such as respiratory failure, septic shock, or acute kidney failure. Early diagnosis and appropriate antibiotic therapy are crucial for reducing the risk of severe outcomes.
- Healthcare Professionals
- Disease Ontology ID - DOID:10457
- Pathophysiology
- Pathophysiology: Legionnaires' disease is a severe form of pneumonia caused by the bacterium Legionella pneumophila. The bacterium is typically inhaled in aerosolized water droplets. Once in the lungs, Legionella bacteria are phagocytized by alveolar macrophages but can evade the immune response by preventing the fusion of phagosomes with lysosomes. This allows the bacteria to replicate within the macrophages, leading to cell lysis and the release of more bacteria. The host immune response to the infection includes the recruitment of neutrophils and the release of inflammatory cytokines, contributing to lung tissue damage and resulting in pneumonia characterized by alveolar inflammation and consolidation.
- Carrier Status
- Legionnaires' disease is not associated with a carrier status. It is a type of pneumonia caused by the Legionella bacteria, typically found in freshwater environments. The disease is contracted through inhalation of contaminated water droplets, not through person-to-person transmission.
- Mechanism
- Legionella spp. enter the lungs either by aspiration of contaminated water or inhalation of aerosolized contaminated water or soil. In the lung, the bacteria are consumed by macrophages, a type of white blood cell, inside of which the Legionella bacteria multiply, causing the death of the macrophage. Once the macrophage dies, the bacteria are released from the dead cell to infect other macrophages. Virulent strains of Legionella kill macrophages by blocking the fusion of phagosomes with lysosomes inside the host cell; normally, the bacteria are contained inside the phagosome, which merges with a lysosome, allowing enzymes and other chemicals to break down the invading bacteria.
- Treatment
- Effective antibiotics include most macrolides, tetracyclines, ketolides, and quinolones. Legionella spp. multiply within the cell, so any effective treatment must have excellent intracellular penetration. Current treatments of choice are the respiratory tract quinolones (levofloxacin, moxifloxacin, gemifloxacin) or newer macrolides (azithromycin, clarithromycin, roxithromycin). The antibiotics used most frequently have been levofloxacin, doxycycline, and azithromycin.Macrolides (azithromycin) are used in all age groups, while tetracyclines (doxycycline) are prescribed for children above the age of 12 and quinolones (levofloxacin) above the age of 18. Rifampicin can be used in combination with a quinolone or macrolide. Whether rifampicin is an effective antibiotic to take for treatment is uncertain. The Infectious Diseases Society of America does not recommend the use of rifampicin with added regimens. Tetracyclines and erythromycin led to improved outcomes compared to other antibiotics in the original American Legion outbreak. These antibiotics are effective because they have excellent intracellular penetration in Legionella-infected cells. The recommended treatment is 5–10 days of levofloxacin or 3–5 days of azithromycin, but in people who are immunocompromised, have severe disease, or other pre-existing health conditions, longer antibiotic use may be necessary. During outbreaks, prophylactic antibiotics have been used to prevent Legionnaires' disease in high-risk individuals who have possibly been exposed.The mortality at the original American Legion convention in 1976 was high (29 deaths in 182 infected individuals) because the antibiotics used (including penicillins, cephalosporins, and aminoglycosides) had poor intracellular penetration. Mortality has plunged to less than 5% if therapy is started quickly. Delay in giving the appropriate antibiotic leads to higher mortality.
- Compassionate Use Treatment
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Legionnaires' disease is typically treated with antibiotics, such as macrolides (e.g., azithromycin) or fluoroquinolones (e.g., levofloxacin). For compassionate use or off-label treatments, various options may be considered based on the severity of the disease and the specific patient's situation. Some potential off-label or experimental treatments could include:
1. **Rifampin**: Sometimes used in combination with other antibiotics for severe cases, although it is not the first-line treatment.
2. **Tigecycline**: A broad-spectrum antibiotic that might be considered in cases where standard treatments are ineffective.
3. **Monoclonal antibodies**: These are in experimental stages and aim to boost the immune response to infections.
4. **IVIG (Intravenous Immunoglobulin)**: Especially in severe or resistant cases, although it remains experimental.
Such treatments would typically be considered only by medical professionals in specialized or severe cases under appropriate regulatory guidance. - Lifestyle Recommendations
-
For individuals looking to decrease their risk of Legionnaires' disease, the following lifestyle recommendations are advised:
1. **Maintain Proper Hygiene:**
- Regularly clean and disinfect water systems, such as hot tubs, humidifiers, and air conditioning units, especially in homes and workplaces.
2. **Avoid Potential Sources:**
- Be cautious around mist-producing devices, such as decorative fountains or large air-conditioning systems, particularly if you're immunocompromised or have pre-existing lung conditions.
3. **Consider Smoking Cessation:**
- Smoking damages the lungs and can increase susceptibility to respiratory infections, including Legionnaires’ disease.
4. **Improve Immune Function:**
- Maintain a healthy diet, exercise regularly, and get adequate sleep to strengthen your immune system.
5. **Professional Inspections:**
- Schedule regular inspections and maintenance of water systems in buildings, especially in places like hotels, hospitals, and long-term care facilities.
6. **Stay Informed During Travel:**
- When staying in hotels or using public facilities, be aware of any reported outbreaks and avoid spas, pools, or other water systems if an outbreak is known.
Implementing these recommendations can help minimize the risk of contracting Legionnaires' disease. - Medication
-
Legionnaires' disease is typically treated with antibiotics. The choice of antibiotic depends on the severity of the infection and patient-specific factors. Commonly used antibiotics include:
1. **Azithromycin**: Often used as a first-line treatment.
2. **Levofloxacin**: Another common first-line treatment.
3. **Doxycycline**: An alternative option, particularly for patients who may not tolerate azithromycin or levofloxacin.
4. **Ciprofloxacin**: Used less frequently but can be effective.
The course of treatment can vary but generally lasts from 7 to 14 days. Hospitalization might be required for severe cases. Early diagnosis and prompt antibiotic treatment are crucial for reducing the risk of complications and improving outcomes. - Repurposable Drugs
-
Repurposable drugs for Legionnaires' disease primarily include antibiotics that are effective against the bacterium Legionella pneumophila. These include:
1. **Macrolides**
- Azithromycin
- Clarithromycin
2. **Fluoroquinolones**
- Levofloxacin
- Moxifloxacin
These antibiotics are used because they target the bacteria responsible for the infection, providing effective treatment. - Metabolites
- Legionnaires' disease, caused by *Legionella* bacteria, primarily affects the lungs and is a type of pneumonia. While specific metabolites unique to Legionnaires’ are not typically the focus, metabolic alterations due to the infection may involve inflammatory markers and changes in respiratory function. Nanotechnology is not typically mentioned as a direct factor in Legionnaires' disease, although advanced detection methods using nanotechnology could potentially aid in faster diagnosis and treatment.
- Nutraceuticals
- Nutraceuticals are foods or dietary supplements that provide health benefits, but there is limited evidence supporting their effectiveness in treating or preventing Legionnaires' disease. This condition is a type of pneumonia caused by the Legionella bacteria and is typically treated with antibiotics. Nutraceuticals are unlikely to replace conventional medical treatments for Legionnaires' disease.
- Peptides
- Legionnaires' disease is a severe form of pneumonia caused by the bacterium Legionella pneumophila. This bacterium can be found in freshwater environments but becomes a health concern when it grows and spreads in human-made water systems, such as cooling towers or plumbing systems in large buildings. Common symptoms include cough, fever, chills, muscle aches, and headaches. Treatment typically involves antibiotics like fluoroquinolones or macrolides. It's crucial to diagnose and treat Legionnaires’ disease promptly to prevent severe complications and improve outcomes.