Other Names : Legionella pneumonia; Pontiac fever
Definition:–
Legionellosis is an 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.
The bacteria that cause Legionnaire’s disease have been found in water delivery systems. They can survive in the warm, moist, air conditioning systems of large
buildings, including hospitals.
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Lung tissue during legionellosis.
Most cases are caused by Legionella pneumophila. The rest of the cases are caused by other Legionella species.
Spread of the bacteria from person to person has not been proven.
Most infections occur in middle-aged or older people, although they have been reported in children. Typically, the disease is less severe in children.
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 caused by the same bacterium but produces a milder respiratory illness without pneumonia that resembles acute influenza
Legionnaires’ disease acquired its name in July 1976 when an outbreak of pneumonia occurred among people attending a convention of the American Legion in
Philadelphia. On January 18, 1977 the causative agent was identified as a previously unknown bacterium, subsequently named Legionella. Some people can be infected
with the Legionella bacterium and have only mild symptoms or no illness at all.
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.
Signs and symptoms:-
Symptoms tend to get worse during the first 4 – 6 days. They typically improve in another 4 – 5 days.
Symptoms may include:……….
•Chest pain
•Coughing up blood
•Fever
•Gastrointestinal symptoms, such as diarrhea, nausea, vomiting, and abdominal pain
•General discomfort, uneasiness, or ill feeling (malaisemalaise)
•Headache
•Joint pain
•Lack of coordination (ataxiaataxia)
•Loss of energy
•Muscle aches and stiffness
•Nonproductive cough
•Shaking chills
•Shortness of breath
Laboratory tests may show that patients’ renal functions, liver functions and electrolytes are deranged, including hyponatremia. Chest X-rays often show pneumonia
with bi-basal consolidation. It is difficult to distinguish Legionnaires’ disease from other types of pneumonia by symptoms or radiologic findings alone; other tests
are required for diagnosis.
Persons with Pontiac fever experience fever and muscle aches without pneumonia. They generally recover in 2 to 5 days without treatment.
The time between the patient’s exposure to the bacterium and the onset of illness for Legionnaires’ disease is 2 to 10 days; for Pontiac fever, it is shorter,
generally a few hours to 2 days.
Cause:-
L. pneumophila is specifically considered as a pathogen of the respiratory tract. Other infections have also been reported, including haemodialysis fistulae,
pericarditis, and wound and skin infections. Bacteraemia is often associated with Legionnaires’ disease. Intestinal infections may only occur as part of respiratory
infections, and where gastrointestinal symptoms have on occasion been described.
No animal infections have been specifically recorded.
Infections of protozoa such as Hartmannella vermiformis and related protozoa have been shown to be able to support the growth of L. pneumophila in tap water. Also
Acanthamoeba, Naegleria and Tetrahymena can be infected by L. pneumophila. pathway may be how these organisms survive in the environment.
Risk Factor:–
•Lung failure
•Death
Transmission:-
Legionellosis infection normally occurs after inhaling an aerosol (suspension of fine particles in air) containing Legionella bacteria. Such particles could
originate from any infected water source. When mechanical action breaks the surface of the water, small water droplets are formed, which evaporate very quickly. If
these droplets contain bacteria, the bacteria cells remain suspended in the air, invisible to the naked eye but small enough to be inhaled into the lungs. This often
occurs in poorly ventilated areas such as prisons where a condensating air conditioner can spread it throughout the entire room, infecting anyone not immune to the
strain of bacteria. Potential sources of such contaminated water include cooling towers used in industrial cooling water systems as well as in large central air
conditioning systems, evaporative coolers, hot water systems, showers, windshield washers, whirlpool spas, architectural fountains, room-air humidifiers, ice making
machines, misting equipment, and similar disseminators that draw upon a public water supply. The disease may also be spread in a hot tub if the filtering system is
defective. Freshwater ponds, creeks, and ornamental fountains are potential sources of Legionella. The disease is particularly associated with hotels, cruise ships
and hospitals with old, poorly maintained pipework and cooling systems. A study published by the European Journal of Epidemiology points to automotive windshield
washing systems as a source, recommending the addition of an antibacterial agent to the system’s reservoir.In several cases Compost sparks Legionnaire’s fear as
well.
Breeding ground:–
The bacteria grow best in warm water, like the kind found in hot tubs, cooling towers, hot water tanks, large plumbing systems, or parts of the air-conditioning
systems of large buildings. Indoor ornamental fountains have been confirmed as a cause of Legionnaires’ disease outbreaks. In all documented cases submerged lighting
as a heat source was attributed to the outbreak. Controlling the growth of Legionella in ornamental fountains is touched on in many of the listed guidelines.
However, specific guidelines for ornamental fountains have also been published.
You may click to learn about Legionella bacteria and How to control it
Diagnosis:–
People of any age may suffer from Legionnaires’ disease, but the illness most often affects middle-age and older persons, particularly those who smoke cigarettes or
have chronic lung disease. Immunocompromised patients are also at elevated risk. Pontiac fever most commonly occurs in persons who are otherwise healthy.
The most useful diagnostic tests detect the bacteria in sputum, find Legionella antigens in urine samples, or the comparison of Legionella antibody levels to in two
blood samples taken 3 to 6 weeks apart. A urine antigen test which is simple, quick, and very reliable will only detect Legionella pneumophila serogroup 1. In
addition the urine antigen test will not identify the specific subtypes so it cannot be used to match the patient with the environmental source of infection.
Exams and Tests:-
The health care provider will perform a physical exam, and may hear abnormal sounds called crackles when listening to the chest with a stethoscope.
Tests that may be done include:
•Arterial blood gasesArterial blood gases
•Chest x-rayChest x-ray
•Complete blood count (CBCCBC), including white blood cell countwhite blood cell count
•Erythrocyte sedimentation rateErythrocyte sedimentation rate
•Liver function testsLiver function tests
•Sputum cultureSputum culture for the Legionella bacteria
•Sputum indirect fluorescent antibody test for the Legionella bacteria
•Urine tests to check for Legionella pneumophila bacteria
Treatment:–
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.
Antibiotics are used to fight the infection. Treatment is started as soon as Legionnaire’s disease is suspected, without waiting for confirmation by lab test.
Other treatments may include:
•Fluid and electrolyteelectrolyte replacement
•Oxygen (given through a mask or breathing machine)
Prognosis:
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.
Legionnaire’s disease can be life-threatening. The death rate is higher in patients with other diseases. The death rate for patients who develop Legionnaire’s
disease while in the hospital is close to 50%, especially when antibiotics are started late.
Legionnaire’s disease can be life-threatening. The death rate is higher in patients with other diseases. The death rate for patients who develop Legionnaire’s
disease while in the hospital is close to 50%, especially when antibiotics are started late.
Prevention:
Treating water delivery systems can prevent the spread of disease.
Various studies have shown that some 40% to 60% of cooling towers tested contained Legionella.
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 wiper water. The finding came after researchers
spotted that professional drivers are five times more likely to be infected.
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): Legionellae die within 32 minutes
*At 55 °C (131 °F): Legionellae 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): Legionellae growth range
*Below 20 °C (68 °F): Legionellae can survive but are dormant
Removing slime may be an effective control process.
Outbreaks:-
Philadelphia, United States, 1976
The first recognized outbreak occurred on July 27, 1976 at the Bellevue Stratford Hotel in Philadelphia, Pennsylvania, where members of the American Legion, a United
States military veterans association, had gathered for the American Bicentennial. Within two days of the event’s start, veterans began falling ill with a
then-unidentified pneumonia. They were tachypneic and complained of chest pain. As many as 221 people were given medical treatment, and 34 deaths occurred. At the
time, the U.S. was debating the risk of a possible swine flu epidemic, and this incident prompted the passage of a national swine flu vaccination program. That cause
was ruled out, and research continued for months, with various theories discussed in scientific and mass media that ranged from toxic chemicals to terrorism
(domestic or foreign) aimed at the veterans.
The U.S. Centers for Disease Control and Prevention mounted an unprecedented investigation and, by September, the focus had shifted from outside causes, such as a
disease carrier, to the hotel environment itself. In January 1977, the Legionellosis bacterium was finally identified and isolated, and found to be breeding in the
cooling tower of the hotel’s air conditioning system, which then spread it through the entire building. This finding prompted new regulations worldwide for climate
control systems.
United Kingdom, 1985
In April 1985, 175 patients were admitted to the District or Kingsmead Stafford Hospitals with chest infection or pneumonia. 28 died. The medical diagnosis showed
that this was Legionnaires’ disease and the immediate epidemiological investigation traced the source of the infection to the air-conditioning cooling tower on the
roof of the Stafford District Hospital. A Government Inquiry was set up to investigate how the infection occurred and why it became Britain’s largest epidemic of
Legionnaires’ disease. The infection was linked to one small zone in the hospital: the outpatients department. The initial investigation searched for engineering
reasons to explain why this particular zone was the risk area. More detailed and wider epidemiological surveys subsequently showed that staff working in the whole
area supplied with fresh air taken adjacent to the tower, had antibodies to the disease. The outpatients department was unique in having a very large transient
population of susceptible individuals either receiving treatment or accompanying friends.
Netherlands, 1999
In March 1999, an outbreak in the Netherlands occurred during a flower exhibition in Bovenkarspel. 200 people became ill and at least 32 people died. There is a
possibility that more people died from it, but these people were buried before the Legionella infection was recognized. The source of the bacteria were probably a
whirlpool and a humidifier in the exhibition area.
Melbourne, Australia, 2000
In April 2000, an outbreak of Legionella pnemophila serogroup 1 occurred in Melbourne, Australia. The outbreak resulted in 125 confirmed cases of Legionnaire’s
disease, with 95 (76%) hospitalised. It is reported that 4 died from the outbreak. The investigation traced the source of the infection to the cooling tower at the
newly opened aquarium. Since this outbreak, legionella infection statistics are required to be reported by the state government as a notifiable disease.[35]
Stringent Regulations were introduced by the State to control legionella in 2001.
Spain, 2001
The world’s largest outbreak of Legionnaires’ disease happened in July 2001 (patients began appearing at the hospital on July 7), in Murcia, Spain. More than 800
suspected cases were recorded by the time the last case was treated on July 22; 636–696 of these cases were estimated and 449 confirmed (so, at least 16,000 people
were exposed to the bacterium) and 6 died (a case-fatality rate of approximately 1%).
A case-control study matching 85 patients living outside the city of Murcia with two controls each was undertaken to identify the outbreak source; the
epidemiological investigation implicated the cooling towers at the Morales Meseguer Hospital. An environmental isolate from these towers with an identical molecular
pattern as the clinical isolates was subsequently identified and supported that epidemiologic conclusion.
United Kingdom, 2002
Main article: 2002 Barrow-in-Furness Legionnaires’ disease outbreak
In 2002, Barrow-in-Furness in the U.K. suffered an outbreak of Legionnaires’ disease. Six women and one man died as a result of the illness; another 172 people also
contracted the disease. The cause was found to be a contaminated cooling tower at the town’s Forum 28 arts centre. Barrow Borough Council later became the first
public body in the UK to be charged with corporate manslaughter but were cleared. They were, however, along with architect Gillian Beckingham, fined for breaches of
Health and Safety regulations in a trial that ended in 2006.
Norway, 2005
In Fredrikstad, Norway, 56 people became ill and ten died from Legionnaires’ disease caused by bacteria growing in an air scrubber of a nearby factory.
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.
Resources:
http://www.nlm.nih.gov/medlineplus/ency/article/000616.htm
http://en.wikipedia.org/wiki/Legionellosis
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