Legionellosis

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(Redirected from Legionnaire's Disease)

Template:DiseaseDisorder infobox | }} Legionellosis is an infection caused by the genus of Gram negative bacteria Legionella, notably L. pneumophila. At least 46 species and 70 serogroups have been identified. L. pneumophila, a ubiquitous aquatic organism that thrives in warm environments (25 to 45 °C with an optimum around 35 °C) causes over 90 % of Legionnaires Disease.

The disease has two distinct forms:

  • Legionnaires' disease is the name for the more severe form of infection which includes pneumonia
  • Pontiac fever is a milder respiratory illness without pneumonia caused by the same bacterium

Legionnaires' disease acquired its name in 1976 when an outbreak of pneumonia occurred among people attending a convention of the American Legion in Philadelphia. On January 18, 1977 scientists identified the causative agent as a previously unknown bacterium, subsequently named Legionella.

An estimated 8,000 to 18,000 people get Legionnaires' disease in the United States each year. Some people can be infected with the Legionella bacterium and have mild symptoms or no illness at all.

Outbreaks of Legionnaires' disease receive significant media attention. However, this disease usually occurs as a single, isolated case not associated with any recognized outbreak. When outbreaks do occur, they are usually recognized in the summer and early fall, but cases may occur year-round. Legionnaires' disease is fatal for about 5% to 30% of individuals.

Contents

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Symptoms

Patients with Legionnaires' disease usually have fever, chills, and a cough, which may be dry or may produce sputum. Some patients also have muscle aches, headache, tiredness, loss of appetite, and, occasionally, diarrhea. Laboratory tests may show that patients' kidneys are not functioning properly. Chest X-rays often show pneumonia. 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.

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Infections

Intestinal Infections: These may only occur as part of respiratory infections, where gastrointestinal symptoms have on occasion been described.

Extraintestinal Infections: L. pneumophila is specifically considered as a pathogen of the respiratory tract, where it is a cause of atypical pneumonia, also known as Legionnaires' disease. Other infections have also been reported, including haemodialysis fistulae, pericarditis and wound and skin infections. Bacteraemia is often associated with Legionnaires' disease.

One species Legionella longbeachae is contracted via inhaling infected compost or soil.

Animal Infections: None specifically recorded.

Infections of Protozoa: Protozoa such as Harmanella 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. This pathway may be how these fastidious organisms survive in the environment.

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Diagnosis

The most useful tests detect the bacteria in sputum, find Legionella antigens in urine samples, or compare antibody levels to Legionella in two blood samples obtained 3 to 6 weeks apart. The urine antigen test is simple, quick, and very reliable; however it will only detect legionella pneumophila serogroup #1. Also the urine antigen test will not identify the specific subtyping so it cannot be used to match the patient with the environmental source of infection.

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Who gets legionellosis?

People of any age may get Legionnaires' disease, but the illness most often affects middle-aged 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.

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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.
Rifampin can be used in combination with a quinolone or macrolide. Tetracyclines and erythromycin led to improved outcome compared to other antibiotics in the original American Legion outbreak. These antibiotics are effective because they have excellent intracellular penetration since 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.

Pontiac fever requires no specific antibiotic treatment.

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How is legionellosis spread?

Legionellosis infection occurs after persons have breathed mists that come from a water source (e.g., air conditioning cooling towers, whirlpool spas, showers) contaminated with Legionella bacteria. Persons may be exposed to these mists in hotels, workplaces, hospitals, or public places. Legionellosis is not passed from person to person, and there is no evidence of persons becoming infected from auto air conditioners or household window air-conditioning units.

Legionella longbeachae, one species in the Legionella family, is found in soils and compost. Persons inhaling soil or compost dust containing Legionella longbeachae risk contracting the disease. Thus, an additional risk source can be pre-purchased bags of soil, compost, or potting mix.

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Where is the Legionella bacterium found?

Legionella organisms can be found in many types of water systems. The bacteria will grow in water temperatures from 68° F to 124 °F (20 °C to 50 °C). However, the bacteria reproduce at the greatest rate in warm(90 - 105 °F, 32 - 40 °C), stagnant water, such as that found in certain plumbing systems and hot water tanks, cooling towers and evaporative condensers of large air-conditioning systems, whirlpool spas and ornamental fountains. New guidelines for ornamental fountains (Dec 2005) can be found at http://www.legionellarm.com. Patients have been infected through exposure to contaminated aerosols generated by cooling towers, showers, faucets, respiratory therapy equipment, and room-air humidifiers. Cases of legionellosis have been identified worldwide. Several European countries established a working group in 1986 known as EWGLI (http://www.ewgli.org) to share knowledge and experience. In 1987, EWGLI established the EWGLINET surveillance scheme to provide a capability within the European Union for the detection, prevention and control of cases and outbreaks of legionnaires' disease that may have been acquired as a result of travelling within Europe and staying in public accommodation sites.

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Prevention

Improved design, operation, maintenance and implementation of risk management strategies for cooling towers, potable water systems and other aerosolizing equipment to limit the growth and spread of Legionella organisms are the foundations of legionellosis prevention.

During outbreaks epidemiological investigators from CDC and local health departments as well as independent legionella engineering / environmental investigators seek to identify the source of disease transmission and recommend appropriate prevention and control measures. The key recommendation for legionella control is development and implementation of a Legionella Risk Management plan which includes as a first step an engineering assessment of the water system and equipment contained in that system.

In September 2004, it was revealed in an article in the magazine "Science" that the complete genome of Legionella pneumophila has been unraveled. This will help researchers to find out how exactly the bacterium works and how people can be protected against infection.

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Frequency of Cleaning

Cooling towers should be cleaned and disinfected at least twice a year. Normally this maintenance will be performed before initial start-up at the beginning of the cooling season and after shut-down in the fall. Systems with heavy bio-fouling or high levels of Legionella may require additional cleaning. Any system that has been out of service for an extended period should be cleaned and disinfected. New systems require cleaning and disinfecting because construction material residue can contribute to Legionella growth.

After a cooling tower has been drained and cleaned, some experts recommend an 'on line' disinfection using a minimum of 5 ppm free halogen residual while running the pumps for at least 6 hours before operating the fans.

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Wisconsin Protocol

Emergency decontamination protocols describing cleaning procedures and hyperchlorination for cooling towers have been developed for towers implicated in the transmission of legionellosis. If cooling towers or evaporative condensers are implicated in health-care–associated legionellosis, decontaminate the cooling-tower system.

Acceptable cleaning procedures include those described in the Wisconsin Protocol. This procedure calls for an initial shock treatment with 50 ppm free residual (total) chlorine, addition of detergent to disperse bio-fouling, maintenance of 10 ppm chlorine for 24 hours, and a repeat of the cycle until there is no visual evidence of biofilms. To prevent exposure during cleaning and maintenance, proper personal protective equipment should be worn: a Tyvek-type suit with a hood, protective gloves, and a properly fitted respirator with a high-efficiency particulate (HEPA) filter or a filter effective at removing one-micrometre particles.

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Design - Best Practices Guide for Cooling Towers

High-efficiency drift eliminators are essential for all cooling towers. Cross-flow cooling tower drift eliminators rated at 0.005% drift rates are available for retro-fits of existing towers. Counter-flow cooling tower drift eliminators rated at 0.001% drift rates are available for retro-fits of existing towers. Older systems can usually be retrofitted with high-efficiency models. A well-designed and well-fitted drift eliminator can greatly reduce water loss and potential for exposure. Other important design features include easy access or easily disassembled components to allow cleaning of internal components including the packing (fill). Enclosure of the system will prevent unnecessary drift of water vapor, and other design features to minimize the spray generated by these systems are also desirable.

The fiberglass and stainless steel cooling towers are rated for higher levels of chlorine than the galvanized towers. Some manufactures recommend that their galvanized cooling towers not be exposed to chlorine levels above 1 ppm. There was a report of a trend in Europe to install more heat exhangers and fewer cooling towers because of the risks of Legionella.

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Design - Best Practices Guide for Potable Water Systems

Historically cooling towers and air conditioning systems have been considered the prime culprit in legionnaires' disease outbreaks. Studies have shown that over 90% of outbreaks in hospitals, hotels and office buildings are related to potable water systems.

In order to control pathogens, the hot water supply and return systems must be balanced hydraulically and this hydraulic balancing must be maintained and monitored. The supply and return system must be kept running 24 hours a day. Similar to the human vascular system, the hot water system requires continuous flow to all parts without any exception. Low or no flow in only one part of the system can result in the formation of deposition and biofilm that can lead to nosocomial infections.

Placing a 5 or 10 micrometre filter on the incoming cold water main would reduce the amount of sediment entering the system dramatically. This size filter will not stop bacteria, but it will reduce significantly the amount of solids that provide nutrients and assist in biofilm development. Even a 25 to 50 micrometre filter would have a significant effect on sediment reduction with very little initial cost. Media filters will retain bacteria and can provide a growth environment. Filters without media that are self flushing are recommended.

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Legionellae and temperature

  • Below 68 °F: Legionellae can survive but are dormant
  • 68 to 122 °F (20 to 50°C): Legionellae growth range
  • 95 to 115 °F (35 to 46°C): Ideal growth range
  • Above 122 °F (50 °C): They can survive but do not multiply
  • At 131 °F (55 °C): Legionellae die within 5 to 6 hours
  • At 140 °F (60 °C): Legionellae die within 32 minutes
  • At 151 °F (66 °C): Legionellae die within 2 minutes
  • 158 to 176 °F (70 to 80 °C): Disinfection range
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Significant Outbreaks

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Philadelphia, 1976

The original outbreak occurred in July 1976 at the Bellevue Stratford Hotel, Broad and Walnut 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. Numbers differ, but perhaps as many as 221 persons were given medical treatment; 34 died. At the time, the US 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 US Centers for Disease Control mounted an unprecedented investigation. By September, the focus 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. [1]

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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. Probably more people died from it, but these were buried before the Legionella infection was recognized. The source of the bacteria were probably a whirlpool and a moisturizer in the exhibition area.

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Spain, 2001

The world's largest outbreak of Legionnaries' disease happened in July 2001 (the patients began to go to the hospital on July 7), in Murcia, Spain, where more than 800 suspected cases were recorded by July 22, when the last case was treated; 636–696 of these cases were estimated and 449 confirmed (so, at least 16,000 persons were exposed to the bacterium) and 6 dead (this is a case-fatality rate of approximately 1%.).

A controlled case study matching 85 patients living outside the city of Murcia with two controls each was undertaken to identify the outbreak source; the epidemiologic investigation implicated the cooling towers at a city hospital (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.

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Norway, 2001

The first known case of the disease discovered in Norway occurred in 2001. 28 people were infected in the city of Stavanger, and seven people died. At first the authorities were puzzled as several of the victims lived all around the country, including one in Germany and another in England. After a massive hunt the source of the outbreak turned out to be the small lake of Breiavatnet, which has a fountain in the middle of it. The fountain had sprayed the bacteria into the air, in turn getting picked up by a cooling system at a Stavanger hotel close by. Only three of the infected had stayed at the hotel but it turned out the exit shaft of the cooling tower was right next to a public bus stop, explaining the other victims.

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United Kingdom, 2002

In 2002 Barrow suffered the UK's worst outbreak of legionnaires' disease. Six women and one man died as a result of the illness, another 172 people also contracted the disease. The caused was found to be faulty air conditioning at the town's Forum 28 arts centre.

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Norway, 2005

In May 2005 there was a second—greater—outbreak in Norway, this time originating in the southeastern town of Fredrikstad. As of 8 June 2005, 52 patients were confirmed infected and ten people were dead. The dead were all from Fredrikstad or nearby cities, in age ranging from 68 to early 90's. The source of the outbreak unexpectedly came from an air scrubber (an industrial air purification facility; this particular one operated by Borregaard Industries in Sarpsborg). Such an installation has never before been reported as a source of Legionellosis anywhere in the world. Although the source was finally identified by DNA matching, it was also fairly well identified by analysing risk increases from people living near suspected sources.

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Toronto, 2005

In October 2005 at least 21 people have died and over 100 fallen ill during an outbreak at the Seven Oaks Home for the Aged in Toronto, Ontario, Canada. Legionnaire's disease was originally ruled out as being the cause, but post-mortem examinations confirmed that victims had legionella bacteria in their lungs. The outbreak is still being investigated, and researchers believe this particular outbreak may be related to a new strain of the bacteria. [2]. Since October 4, two additional cases of the disease have been reported by residents of the area who had never visited Seven Oaks. This has investigators puzzled, and they believe that a faulty cooling tower at Seven Oaks may have not only caused residents of the home to fall ill, but also people walking nearby outside. [3]

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Images

  • legionella.jpg
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References

  • Harrison's textbook of medicine and Mandell's infectious disease textbook (5th edition), New Engl J Med 1997
  • Template:Cite book
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External links

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External links: Cooling towers

da:Legionærsyge de:Legionärskrankheit es:Legionelosis fr:Légionellose nl:Veteranenziekte no:Legionærsyken nn:Legionærsjuke pt:Doença do legionário sv:Legionärssjuka zh:退伍軍人症

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