Legionnaires’ disease is a severe form of pneumonia. It is a potentially fatal infectious disease caused by Gram negative, 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).
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People usually get it by breathing in mist from water that contains the bacteria. The mist may come from hot tubs, showers or air-conditioning units for large buildings. The bacteria don’t spread from person to person.
Older adults, smokers and people with weakened immune systems are particularly susceptible to Legionnaires’ disease.
Legionella bacterium also causes Pontiac fever, a milder illness resembling the flu. Separately or together, the two illnesses are sometimes called legionellosis. Pontiac fever usually clears on its own. But untreated Legionnaires’ disease can be fatal. Although prompt treatment with antibiotics usually cures Legionnaires’ disease, some people continue to experience problems after treatment.
The disease and the bacterium were discovered following an outbreak at an American Legion convention in Philadelphia in 1976, hence the name.
Legionnaires’ disease usually develops two to 14 days after exposure to legionella bacteria. It frequently begins with the following signs and symptoms:
*Fever that may be 104 F (40 C) or higher
By the second or third day, you’ll develop other signs and symptoms that may include:
*Cough, which may bring up mucus and sometimes blood
*Shortness of breath
*Loss of appetite
*Gastrointestinal symptoms, such as nausea, vomiting and diarrhea
*Confusion or other mental changes
Although Legionnaires’ disease primarily affects the lungs, it occasionally can cause infections in wounds and in other parts of the body, including the heart.
A mild form of Legionnaires’ disease — known as Pontiac fever — may produce symptoms including fever, chills, headache and muscle aches. Pontiac fever doesn’t infect lungs, and symptoms usually clear within two to five days.
Legionnaires’ is caused by a bacteria known as Legionella pneumophila.
The bacteria is found widely throughout natural water systems such as rivers and ponds but temperature is critical to its growth and it is in the warm or hot water of artificial water systems such as heating plants or whirlpools that it can really thrive, forming a biofilm or layer of living bacteria over artificial structures.
Other sources include the water systems of large buildings, cooling towers of air conditioning systems, fountains and ponds, and communal showers.
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It used to be thought that people caught Legionella when they breathed in an aerosol or fine mist of contaminated water. But while this may be true in some cases it is now thought that Legionella more commonly occurs when contaminated water in the mouth (drinking water for example) is able to get past the body’s normal defences and passes down into the lungs.
This is known as aspiration and it explains why smokers and those with chronic lung disease are especially vulnerable to Legionella. Normally fluid in the mouth is pushed down the gullet and into the stomach where any particles such as bacteria can be broken down.
The gag reflex prevents water entering into the breathing tubes, and the action of tiny hair-like projections or cilia on the mucosal membranes surface brushes back any particles that have passed towards the lungs.
But in smokers and those with lung disease or weakened immunity these mechanisms may not work properly and bacteria can pass more easily into the lungs to establish a pneumonia.
Occurrences are more common in late summer and early autumn. Men are affected more than women, particularly middle-aged men.
Legionnaires’ disease can lead to a number of life-threatening complications, including:
*Respiratory failure. This occurs when the lungs are no longer able to provide the body with enough oxygen or can’t remove enough carbon dioxide from the blood.
*Septic shock. This occurs when a severe, sudden drop in blood pressure reduces blood flow to vital organs, especially the kidneys and brain. The heart tries to compensate by increasing the volume of blood pumped, but the extra workload eventually weakens the heart and reduces blood flow even further.
*Acute kidney failure. This is the sudden loss of your kidneys’ ability to perform their main function — filtering waste material from your blood.
When your kidneys fail, dangerous levels of fluid and waste accumulate in your body.When not treated effectively and promptly, Legionnaires’ disease may be fatal, especially if your immune system is weakened by disease or medications.
Legionnaires’ disease is similar to other types of pneumonia. To help identify the presence of legionella bacteria quickly, doctor may use a test that checks your urine for legionella antigens — foreign substances that trigger an immune system response. One or more of the following test may also be required:
*A chest X-ray, which doesn’t confirm Legionnaires’ disease but can show the extent of infection in your lungs
*Tests on a sample of your sputum or lung tissue
*A CT scan of your brain or a spinal tap (lumbar puncture) if you have neurological symptoms such as confusion or trouble concentrating
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 and azithromycin. Macrolides are used in all age groups while tetracyclines are prescribed for children above the age of 12 and quinolones above the age of 18. Rifampicin can be used in combination with a quinolone or macrolide. 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 and Legionella infects cells.
The mortality at the original American Legion convention in 1976 was high (34 deaths in 180 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.
According to the journal Infection Control and Hospital Epidemiology, 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
A recent research study provided evidence that Legionella pneumophila, the causative agent of Legionnaires’ disease, can travel airborne at least 6 km from its source. It was previously believed that transmission of the bacterium was restricted to much shorter distances. A team of French scientists reviewed the details of an epidemic of Legionnaires’ disease that took place in Pas-de-Calais in northern France in 2003–2004. There were 86 confirmed cases during the outbreak, of whom 18 died. The source of infection was identified as a cooling tower in a petrochemical plant, and an analysis of those affected in the outbreak revealed that some infected people lived as far as 6–7 km from the plant.
A study of Legionnaires’ disease cases in May 2005 in Sarpsborg, Norway concluded that: “The high velocity, large drift, and high humidity in the air scrubber may have contributed to the wide spread of Legionella species, probably for >10 km. “…
In 2010 a study by the UK Health Protection Agency reported that 20% of cases may be caused by infected windscreen washer systems filled with pure water. The finding came after researchers spotted that professional drivers are five times more likely to contract the disease. No cases of infected systems were found whenever a suitable washer fluid was used.
Temperature affects the survival of Legionella as follows:
*70 to 80 °C (158 to 176 °F): Disinfection range
*At 66 °C (151 °F): Legionellae die within 2 minutes
*At 60 °C (140 °F): They die within 32 minutes
*At 55 °C (131 °F): They die within 5 to 6 hours
*Above 50 °C (122 °F): They can survive but do not multiply
*35 to 46 °C (95 to 115 °F): Ideal growth range
*20 to 50 °C (68 to 122 °F): Growth range
*Below 20 °C (68 °F): They can survive but are dormant
Removing slime, which can carry legionellae when airborn, may be an effective control process
Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose