LEGIONELLA - World Health Organization

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Figure 5.1 Configuration of typical cooling towers and evaporative condensers a) b) Air in Hot water in Air in Water Wet deck surface Drift eliminators (a) Typical cross-flow cooling tower Warm air Warm air out Cold water basin Sump Cooled water out Warm air out Water distribution system Fan (b) Typical counterflow closed-circuit evaporative condenser Source: artwork courtesy of Baltimore Aircoil Co. Warm air Hot water in Water Fluid in Fluid out Spray pump Air in Air inlet louvres 0 <strong>LEGIONELLA</strong> AND THE PREVENTION OF LEGIONELLOSIS
5.1.1 Cross-flow cooling towers As shown in Figure 5.1(a), cooling towers are heat exchangers; they act by cooling water that is in direct contact with the air moving through the tower. Most towers use a medium, referred to as “fill” or “pack”, to maximize the surface area of water in contact with air and therefore available for evaporation. Water from the cooling tower is piped from the tower to a condenser (or other heat source), where it is heated. Warm water is distributed via a spray, or a trough and gutter system at the top of the tower, and falls down over the fill against the countercurrent of air. The warm water is then piped back to the cooling tower to be cooled, and the process is repeated. There may be tens or even hundreds of metres of piping between the tower and the point where the source is cooled. The piping circuit can be quite complex in some industrial settings, where several devices may be cooled. 5.1.2 Counterflow evaporative condensers and cooling towers As shown in Figure 5.1(b), counterflow evaporative condensers and cooling towers are similar to cross-flow cooling towers, except that the warm fluid that is being cooled is contained inside a tubular matrix and does not come into direct contact with the air. The water has only a short circuit from the sump at the base to the distribution system at the top. It then flows down over the tube bundle, in the opposite direction to the airflow, thus cooling the fluid within the tubes. Figure 5.1(b) shows how vapour enters and liquid exits the condenser coil. 5.1.3 Links to outbreaks of legionellosis Cooling towers and evaporative condensers have been implicated in many outbreaks of legionellosis. As discussed in Chapter 1, L. pneumophila serogroup 1 MAb2-reactive strains are the primary legionellae associated with outbreaks of disease from these systems. The causative organism has been readily isolated from many of these devices, usually as a result of neglect or insufficient maintenance (Fields, Benson & Besser, 2002), as illustrated by the example given in Box 5.1. A significant proportion of outbreaks of legionellosis have been attributable to the start-up of stagnant systems without adequate chemical treatment (Bentham & Broadbent, 1993). <strong>LEGIONELLA</strong> AND THE PREVENTION OF LEGIONELLOSIS
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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
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Tables Table 1.1 Main characteristi
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Figure 8.1 Visible biofilm on inter
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Acknowledgements The World Health O
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• John Newbold, Health and Safety
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Executive summary Legionellosis is
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• Health-care facilities — Chap
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Chapter 1 Legionellosis Britt Horne
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Legionnaires’ disease is often in
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1.1.2 Pontiac fever Symptoms Pontia
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Table . Extrapulmonary nfect ons ca
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Proteins produced by the body’s i
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Aspiration may occur in patients wi
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Table . R sk factors for Legionella
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In the outbreak of Legionnaires’
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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 and 64: Chapter 3 Approaches to risk manage
Page 65 and 66: Table . Cool ng tower outbreaks Fac
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: Chapter 5 Cooling towers and evapor
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
Page 115 and 116: For 1999 and 2000, a total of 384 c
Page 117 and 118: 6.3 System assessment This section
Page 119 and 120: Table . Type of colon zat on of wat
Page 121 and 122: 6.4.1 Identify control measures Thi
Page 123 and 124: 6.5.1 Prepare management procedures
Page 125 and 126: Until the situation is under contro
Page 127 and 128: Chapter 7 Hotels and ships Roisin R
Page 129 and 130: F gure . Detected and reported case
Page 131 and 132: Table . Rev ew of outbreaks (more t
Page 133 and 134: 7.2 Water safety plan overview WSPs
Page 135 and 136: The risk of legionellosis is increa
Page 137 and 138: Kingdom to 66% in Spain (Starlinger
Page 139 and 140: Agency, Legionella Section, United
Page 141 and 142: Given the complexity of distributio
Page 143 and 144: 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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