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Legionellosis
 

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 percent of Legionnaires' disease cases.CDC: Etiologic Agent

The disease has two distinct forms:

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. CDC: Incidence 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. The fatality rate of Legionnaires' disease has ranged from 5 to 30 percent during various outbreaks.

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.

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.

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 organisms survive in the environment.

Diagnosis and treatment

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.

The most useful diagnostic 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.

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 percent if therapy is started quickly. Delay in giving the appropriate antibiotic leads to higher mortality.

Pontiac fever requires no specific antibiotic treatment.

How Legionnaires' disease is spread

Legionellosis infection occurs after persons have breathed mists that come from a water source contaminated with Legionella. Potential sources of such contaminated water include cooling towers used in industrial cooling water systems as well as in large central air conditioning systems, domestic hot water systems, showers, whirlpool spas, fountains, room-air humidifiers. and similar disseminators that draw upon a public water supply. Freshwater ponds and creeks are also potential sources of Legionella.

Legionella will grow in water temperatures from 68 °F to 122 °F (20 °C to 50 °C). However, the bacteria reproduce at the greatest rate in stagnant water at temperatures of 95 °F to 115 °F (35 °C to 46 °C).

Legionella longbeachae, a species in the Legionella family, is found in soils and compost. CDC: Potting Soil in CA, OR, WA Thus, the dust from purchased bags of soil, compost, or potting mix is also a potential source of Legionella.

Controlling the potential growth of Legionella in cooling towers

Various studies have shown that some 40 to 60% of cooling towers tested contained Legionella.CTI Legionellosis Guideline: Best Practices for Control of Legionella (WTP-148) (06) A recent research study provided evidence that Legionella pneumophila, the causative agent of Legionnaires' disease, can travel at least 6 km from its source by airborne spread. 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 perished. 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.Long-range transmission of Legionella

Several European countries established a working group known as the European Working Group for Legionella Infections (EWGLI)European Working Group for Legionella Infections to share knowledge and experience about monitoring potential sources of Legionella. That group has published guidelines about the actions to be taken to limit the number of colony forming units (i.e., the aerobic count) of micro-organisms per mL at 30°C (minimum 48 hours incubation):

Aerobic countAction required
10,000 or lessSystem under control.
more than 10,000
up to 100,000		Review program operation. The count should be confirmed by immediate re-sampling. If a similar count is found again, a review of the control measures and risk assessment should be carried out to identify any remedial actions.
more than 100,000Implement corrective action. The system should immediately be re-sampled. It should then be ‘shot dosed’ with an appropriate biocide, as a precaution. The risk assessment and control measures should be reviewed to identify remedial actions.

Temperature affects the survival of Legionellae as follows:What is Legionnaires' Disease?

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

Guidelines for control of Legionella in cooling towers

Many governmental agencies, cooling tower manufacturers and industrial trade organizations have developed design and maintenance guidelines for preventing or controlling the growth of Legionella in cooling towers. Below is a list of sources for such guidelines:

The guidance issued by the UK government's Health and Safety Executive (HSE) now recommends that microbiological monitoring for wet cooling systems, using a dip slide, should be performed weekly.UK: Health and Safety Executive Microbiological monitoring (weekly dip slide)

Outbreaks of Legionnaires' disease

Below is a list of Legionnaires' disease outbreaks, followed by a discussion of many of them:

Suspected Source  Cases   Deaths  Date Location
Cooling tower (unconfirmed)231July 2006Amsterdam, Netherlands
Cooling towers1490June 2006Pamplona, Spain
Cooling tower101February 2006Sydney, Australia
Cooling tower200December 2005Torrevieja, Spain
Cooling tower12721October 2005Toronto, Canada
Cooling tower210June 2005New Rochelle, NY, USA
Indoor ornamental fountain171Summer 2005Rapid City, SD, USA
Air scrubber5210May 2005Fredrickstad, Norway
Cooling tower86212004Pas-de-Calais, France
Cooling tower17272002Barrow, UK
Cooling tower2872001Stavenger, Norway
Cooling tower4496July 2001Murcia, Spain
Whirlpool and moisturizer200321999Bovenkarspel, Netherlands
Cooling Tower (widely accepted)221341976Philadelphia, PA, USA

Philadelphia, 1976

The first recognized outbreak occurred in July 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. Numbers differ, but perhaps as many as 221 persons were given medical treatment; 34 died. 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 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.

Some do not believe that the air conditioning was conclusively proven to be the cause of the outbreak. According to Dr. Victor L. Yu, chief of the infectious disease section at the Oakland Veterans Affairs Medical Center in Pittsburgh, researchers still haven't identified the exact source. Legionnaire's Disease First Outbreak Morbidity and Mortality Weekly Report (MMWR), a weekly publication of the US Centers for Disease Control and Prevention (CDC), stated in 1977 that no source was found in this first outbreak of Legionnaires' disease at the Bellevue Stratford HotelMMWR, January 18 1977, (reprinted January 24 1997 Vol 46(03); 50-56) special issue, Epidemiologic Notes and Reports Follow-up on Respiratory Illness --Philadelphia

See also History of Outbreak at Bellevue Stratford Hotel

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.

Spain, 2001

The world's largest outbreak of Legionnaires' 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 percent).

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.

Norway, 2001

The first known case of the disease in Norway occurred in 2001 when 28 people were infected in the city of Stavanger, and seven died. At first the authorities were puzzled as several of the victims lived in other locations, including one in Germany and another in England. After a massive investigation a fountain in the small lake of Breiavatnet was suspected as the source of the outbreak. But the fountain had not sprayed the bacteria into the air, the source was a cooling tower at the nearby SAS Radisson hotel. Only three of the infected had stayed at the hotel, but the exit vent of the cooling tower was at ground level next to a public bus stop, explaining the other victims.

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 cause was found to be a contaminated cooling tower at the town's Forum 28 arts centre.

France, 2004

Researchers found that the Legionnaires disease bacteria spread through the air up to 6 kilometers from a large contaminated cooling tower at a petrochemical plant in Pas-de-Calais in northern France. That outbreak killed 21 of the 86 people with laboratory-confirmed infection.

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.

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. Since October 2005, 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.

References

See also

External links

Images of Legionella bacteria:

  • http://www.repower.ch/INimg/Newsletter/legionella.jpg
  • http://newsimg.bbc.co.uk/media/images/38922000/jpg/_38922367_legionella203.jpg
  • http://www.chemistryquestion.com/images/Question/legionella.jpg
  • http://www.q-net.net.au/~legion/Legionnaires_Disease_Bugs_Of_This_World.htm

Support groups:

Building biology | Infectious diseases | Industrial hygiene

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This article is licensed under the GNU Free Documentation License. It uses material from the "Legionellosis".

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