LEGIONELLA - World Health Organization

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3.1 Environmental exposure and disease There is no established dose–response relationship for Legionella infections, and the concentration of legionellae necessary to cause an outbreak is unknown. Transmission may occur through inhalation, aspiration or directly from contaminated water (e.g. wound infections), from a wide variety of sources, as discussed in Chapter 1. Data on population dynamics indicate that legionellae are not distributed normally within the aquatic environment, and that even when high concentrations of the bacteria are detected, this may not be related to health risk (Kool et al., 1999; Bentham, 2000). Gathering information on population dynamics of Legionella is difficult, because there have been relatively few outbreaks in which the source has been investigated while it was still infectious, and in which no intervention has occurred before sampling. Of the many reports of Legionella outbreaks caused by cooling towers, few provide details of the numbers of legionellae present in the water at the time the tower was infectious. Often, the tower was examined long after the infectious period, and the bacterial population may have changed dramatically in the interim, as shown by the example in Box 3.1. Box . Hosp tal outbreak n wh ch water sampl ng was neffect ve In 1985, an outbreak of legionellosis occurred at Stafford District General Hospital in the United Kingdom. The investigation team was able to isolate L. pneumophila from a piece of sealant in an air handling unit, but not from any water sample (O’Mahony et al., 1990). Presumably, at the time of the outbreak, the cooling water contained high levels of L. pneumophila. However, between the time of the outbreak and the arrival of the investigation team, the cooling water had been shot dosed (given a brief, high-level treatment) with biocide at least twice, and had been diluted by fresh make-up water. Numbers of legionellae would have been reduced considerably by both the biocide and the dilution with fresh water. Low numbers of L. pneumophila were isolated from a sample of the cooling water collected between the shot doses. The sealant from which the investigation team isolated L. pneumophila came from around a chiller battery within the air-conditioning ducting. The position of the sealant meant that it could have been contaminated by aerosols from the cooling tower, but would not have been affected by the biocide additions. 3.1.1 Cooling tower outbreaks In cooling tower outbreaks in the 1980s, numbers of bacteria were often estimated by immunofluorescence rather than by culture. These results may have been unreliable, because the reagents used were polyclonal antibodies, which have questionable specificity; also, the technique detected both dead and live legionellae. However, isolation of legionellae by culture tends to underestimate the numbers of legionellae by at least an order of magnitude. Table 3.1 shows the results of various cooling tower outbreaks in which the towers were sampled while probably still containing infectious legionellae. 0 <strong>LEGIONELLA</strong> AND THE PREVENTION OF LEGIONELLOSIS
Table . Cool ng tower outbreaks Fac l ty, locat on, date British Broadcasting Corporation (BBC), London, UK, 1998 British Aerospace, Bolton, UK, 1998 Community- acquired, Wisconsin, USA Retirement hotel, Los Angeles, USA, July 1988 Two outbreaks of legionellosis from a single tower in Wisconsin, USA, October 1986 Community outbreak, caused by hospital cooling towers in Delaware, USA, 1994 Hotel outbreak in Sydney, Australia April 1993 CFU = colony forming unit Organ sm, concentrat on (CFU/l tre) Comments Reference Up to 10 6 CFU/l by culture, and up to 10 9 CFU/l by immunofluorescence 10 5 CFU)/l by culture, and 10 7 CFU/l by immunofluorescence L. pneumophila serogroup 1 106 in cooling tower L. pneumophila 9 × 10 6 in water from evaporative condenser >1.6 × 10 6 CFU/l (mean of 2 outbreaks), compared to controls (86/99 controls had
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LEGIONELLA AND THE PREVENTION OF LE
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LEGIONELLA AND THE PREVENTION OF LE
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Foreword Legionellosis is a collect
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Contents Foreword . . . . . . . . .
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Chapter 5 Cooling towers and evapor
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Chapter 9 Disease surveillance and
Page 13 and 14: Tables Table 1.1 Main characteristi
Page 15 and 16: Figure 8.1 Visible biofilm on inter
Page 17 and 18: Acknowledgements The World Health O
Page 19 and 20: • John Newbold, Health and Safety
Page 21 and 22: Executive summary Legionellosis is
Page 23 and 24: • Health-care facilities — Chap
Page 25 and 26: Chapter 1 Legionellosis Britt Horne
Page 27 and 28: Legionnaires’ disease is often in
Page 29 and 30: 1.1.2 Pontiac fever Symptoms Pontia
Page 31 and 32: Table . Extrapulmonary nfect ons ca
Page 33 and 34: Proteins produced by the body’s i
Page 35 and 36: Aspiration may occur in patients wi
Page 37 and 38: Table . R sk factors for Legionella
Page 39 and 40: In the outbreak of Legionnaires’
Page 41 and 42: Table . Potent al treatments for d
Page 43 and 44: 1.4.2 Species and serogroups associ
Page 45 and 46: Other causes of infection In Europe
Page 47 and 48: The interaction of virulent legione
Page 49 and 50: 1.5.2 Surface structures involved i
Page 51 and 52: 1.5.4 Host defence The host defence
Page 53 and 54: Chapter 2 Ecology and environmental
Page 55 and 56: L. pneumophila is thermotolerant an
Page 57 and 58: 2.2.3 Environmental factors and vir
Page 59 and 60: Figure 2.1 Biofilm formation Biofil
Page 61 and 62: 2.4 Sources of Legionella infection
Page 63: Chapter 3 Approaches to risk manage
Page 67 and 68: Even when a source reaches a state
Page 69 and 70: The WSP should be prepared in conju
Page 71 and 72: Identify control measures Control m
Page 73 and 74: F gure . Dec mal reduct on t mes fo
Page 75 and 76: Method Advantages D sadvantages Dos
Page 77 and 78: Validate effectiveness of water saf
Page 79 and 80: • clear statements of responsibil
Page 81 and 82: Chapter 4 Potable water and in-buil
Page 83 and 84: The remainder of this chapter provi
Page 85 and 86: 4.3.1 Document and describe the sys
Page 87 and 88: Construction materials — risk fac
Page 89 and 90: Where temperature controls (discuss
Page 91 and 92: 4.4.2 Monitor control measures This
Page 93 and 94: Chapter 5 Cooling towers and evapor
Page 95 and 96: 5.1.1 Cross-flow cooling towers As
Page 97 and 98: water treatments (including chemica
Page 99 and 100: 5.3 System assessment This section
Page 101 and 102: Spray drift — risk factors Even w
Page 103 and 104: The section on control measures for
Page 105 and 106: • periodic or continuous bleed-of
Page 107 and 108: Box . Po nts to be noted when clean
Page 109 and 110: In certain circumstances, samples m
Page 111 and 112: Table . Example documentat on for m
Page 113 and 114: Chapter 6 Health-care facilities Ma
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For 1999 and 2000, a total of 384 c
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6.3 System assessment This section
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Table . Type of colon zat on of wat
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6.4.1 Identify control measures Thi
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6.5.1 Prepare management procedures
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Until the situation is under contro
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Chapter 7 Hotels and ships Roisin R
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F gure . Detected and reported case
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Table . Rev ew of outbreaks (more t
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7.2 Water safety plan overview WSPs
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The risk of legionellosis is increa
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Kingdom to 66% in Spain (Starlinger
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Agency, Legionella Section, United
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Given the complexity of distributio
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Chapter 8 Natural spas, hot tubs an
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Spas “Natural spa”, denotes fac
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Rare cases of Legionnaires’ disea
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Process step P pework Water n hot t
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Hosepipes may sometimes be used to
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Hot tubs that are not effectively d
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Nutrients — control measures Bath
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Various additives may also be used
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• descriptions of any significant
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Table . Examples of m crob olog cal
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Chapter 9 Disease surveillance and
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Exposure histories allow cases to b
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F gure . Invest gat ng a s ngle cas
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Box . (cont nued) Since the incepti
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Country United Kingdom All reported
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F gure . Annual reported cases, - 0
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Training opportunities Trainees in
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Box . Example of terms of reference
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ecause doing anything more could un
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9.4 Case studies This section descr
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9.4.4 Concrete batcher process on a
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Chapter 10 Regulatory aspects David
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• validation of the effectiveness
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• operating conditions, such as t
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10.4.6 Outbreak investigation and n
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hot water (e.g. health-care facilit
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General prevent on Country DW Wp SB
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Country General prevent on DW Wp SB
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Chapter 11 Laboratory aspects of Le
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• detection of the bacterium in t
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Method Sens t v ty (%) PCR • Rapi
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11.2.2 Detecting Legionella antigen
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DFA has been used successfully with
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• Serologic testing can be used f
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Although not all strains can be rel
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Generally, any water source that ma
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During outbreak investigations, swa
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• other Legionella species that d
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Appendix 1 Example of a water syste
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Weekly water system check list Week
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Appendix 2 Example of a 2-week foll
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Travel Work/travel in the UK: ❑ Y
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Checklist of local places Health/sp
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Appendix 3 Example of a national su
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Strictly Confidential 2 Hospital Ac
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Glossary aerobic bacteria Bacteria
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health-care acquired Legionellosis
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surveillance The process of systema
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References Abu KY, Eisenstein BI, E
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Barbaree JM et al. (1987). Protocol
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Blatt SP et al. (1994). Legionnaire
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Byrne B, Swanson MS (1998). Express
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Crespi S (1993). Legionella y legio
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Edelstein PH (1982b). Comparative s
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Falguera M et al. (2001). Nonsevere
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Gaia V et al. (2003). Sequence-base
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Hayden RT et al. (2001). Direct det
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Ingram JG, Plouffe JF (1994). Dange
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Ko KS et al. (2003). Molecular evol
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Loret JF et al. (2003). Comparison
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McEvoy M et al. (2000). A cluster o
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Olaechea PM et al. (1996). A predic
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Regan CM et al. (2003). Outbreak of
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Schulze-Robbecke R, Rodder M, Exner
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Surman SB, Morton LHG, Keevil CW (1
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Tully M, Williams A, Fitzgeorge RB
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Welti M et al. (2003). Development
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