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Infection Control and Hospital Epidemiology (Cambridge University Press (CUP))
Nectar Aintablian et al. 1998
Detection of pathogens in room air and buildings may suggest a possible, indirect association between ventilation and disease transmission (Artenstein et al., 1967; Sawyer et al., 1994; Aintablian, Walpita & Sawyer, 1998; Mastorides et al., 1999; Suzuki et al., 2002, 2003; Booth et al., 2005; Chen & Li, 2008; Huynh et al., 2008).
On page 43
Aintablian N, Walpita P, Sawyer MH. Detection of Bordetella pertussis and respiratory synctial virus in air samples from hospital rooms. Infection Control and Hospital Epidemiology 1998, 19(12):918–923.
Infection Control (Cambridge University Press (CUP))
John D. Anderson et al. 1985
Although there is no single study showing the effectiveness of isolation, there are many reports documenting the efficacy of the various components of isolation, including use of private rooms (Anderson et al., 1985), and protective equipments such as masks, gloves and gowns (Klein, Perloff & Maki, 1989; Maki, 1994; Maloney et al., 1995).
On page 29
Anderson JD et al. Lack of nosocomial spread of Varicella in a pediatric hospital with negative pressure ventilated patient rooms. Infection Control, 1985, 6(3):120–121.
American Journal of Epidemiology (Oxford University Press (OUP))
MALCOLM S. ARTENSTEIN et al. 1967
Detection of pathogens in room air and buildings may suggest a possible, indirect association between ventilation and disease transmission (Artenstein et al., 1967; Sawyer et al., 1994; Aintablian, Walpita & Sawyer, 1998; Mastorides et al., 1999; Suzuki et al., 2002, 2003; Booth et al., 2005; Chen & Li, 2008; Huynh et al., 2008).
On page 43
Artenstein MS et al. Large-volume air sampling of human respiratory disease pathogens. American Journal of Epidemiology, 1967, 85(3):479–485.
parameters, such as the exhaled air velocity, the viscosity of the fluid and the flow path (i.e. through the nose, the mouth or both) (Barker, Stevens & Bloomfield, 2001).
Barker J, Stevens D, Bloomfield SF. Spread and prevention of some common viral infections in community facilities and domestic homes. Journal of Applied Microbiology, 2001, 91:7–21.
Emerging Infectious Diseases (Centers for Disease Control and Prevention (CDC))
Stefano Bassetti et al. 2005
This may be due to a number of reasons, including a poor host immune response to controlling the infection, concomitant diseases or other respiratory infections that increase the degree of shedding of the infectious agent, and environmental factors favourable to the survival of such agents (Bassetti, Bischoff & Sherertz, 2005).
Bassetti S, Bischoff WE, Sherertz RJ. Are SARS superspreaders cloud adults? Emerging Infectious Diseases, 2005, 11(4):637–638.
The Journal of Infectious Diseases (Oxford University Press (OUP))
Timothy F. Booth et al. 2005
Detection of pathogens in room air and buildings may suggest a possible, indirect association between ventilation and disease transmission (Artenstein et al., 1967; Sawyer et al., 1994; Aintablian, Walpita & Sawyer, 1998; Mastorides et al., 1999; Suzuki et al., 2002, 2003; Booth et al., 2005; Chen & Li, 2008; Huynh et al., 2008).
On page 43
Booth TF et al. Detection of airborne severe acute respiratory syndrome (SARS) coronavirus and environmental contamination in SARS outbreak units. Journal of Infectious Diseases, 2005, 191(9):1472–1477.
Aerosol Science and Technology (Informa UK Limited)
Pei-Shih Chen* et al. 2008
Detection of pathogens in room air and buildings may suggest a possible, indirect association between ventilation and disease transmission (Artenstein et al., 1967; Sawyer et al., 1994; Aintablian, Walpita & Sawyer, 1998; Mastorides et al., 1999; Suzuki et al., 2002, 2003; Booth et al., 2005; Chen & Li, 2008; Huynh et al., 2008).
On page 43
Chen PS, Li CS. Concentration profiles of airborne Mycobacterium tuberculosis in a hospital. Aerosol Science and Technology, 2008, 42(3):194–200.
Building and Environment (Elsevier BV)
Q. Chen 1996
Computational fluid dynamics and particle image velocimetry techniques allow the air distribution performance in a room to be modelled (Nielsen, 1974; Chen, 1996; Etheridge & Sandberg, 1996).
On page 35
Chen Q. Prediction of room air motion by Reynolds-stress models. Building and Environment, 1996, 31(3):233–244.
Published data have suggested that sneezing may produce as many as 40 000 droplets between 0.5–12 μm in diameter (Cole & Cook, 1998; Tang et al., 2006) that may be expelled at speeds up to 100 m/s (Wells, 1955; Cole & Cook, 1998), whereas coughing may produce up to 3000 droplet nuclei, about the same number as talking for five minutes (Cole & Cook, 1998; Fitzgerald & Haas, 2005; Tang et al., 2006).
Cole EC, Cook CE. Characterization of infectious aerosols in health care facilities: an aid to effective engineering controls and preventive strategies. American Journal of Infection Control, 1998, 26(4):453–464.
Journal of Fluids Engineering (ASME International)
Brent A. Craven et al. 2006
A higher air temperature directly above the patient’s head (or body, if lying down) will create convective air currents that may entrain potentially infectious air from neighbouring spaces into the higher temperature column rising air above the patient (Craven & Settles, 2006).
Craven A, Settles GS. A computational and experimental investigation of the human thermal plume. Journal of Fluids Engineering, 2006, 128(6):1251–1258.
Infection Control & Hospital Epidemiology (Cambridge University Press (CUP))
Karen M. Dahl et al. 1996
Other problems with mechanical ventilation include the loss of negative pressure differential in isolation rooms due to the opening of the doors; clogged filters; and adjacent, negatively pressurized spaces (Fraser et al., 1993; Dahl et al., 1996; Sutton et al., 1998; Pavelchak et al., 2001; Rice, Streifel & Vesley, 2001).
On page 40
Dahl KM et al. Follow-up evaluation of respiratory isolation rooms in 10 Midwestern hospitals. Infection Control and Hospital Epidemiology, 1996, 17(12):816–818.
Journal of Fluids Engineering (ASME International)
Brian A. Edge et al. 2005
Entrainment of air into neighbouring airspaces may occur during the most innocuous daily activities; for example, as a result of people walking, or the opening of a door between a room and the adjacent corridor or space (Hayden et al., 1998; Edge, Paterson & Settles, 2005; Tang et al., 2005, 2006).
Edge BA, Paterson EG, Settles GS. Computational study of the wake and contaminant transport of a walking human. Journal of Fluids Engineering, 2005, 127(5):967– 977.
PLoS Medicine (Public Library of Science (PLoS))
A. Roderick Escombe et al. 2007
A comparative analysis of mechanical and natural ventilation systems looked at eight hospitals in Lima, Peru (Escombe et al., 2007).
On page 40
Escombe AR et al. Natural ventilation for the prevention of airborne contagion. PloS Medicine, 2007, 4:309–317.
Infection Control and Hospital Epidemiology (JSTOR)
Kevin P. Fennelly et al. 1998
The Wells–Riley equation (Riley, Murphy & Riley, 1978) was used to evaluate the effect of ventilation, filtration and other physical processes on transmission through droplet nuclei (Nardell et al., 1991; Fennelly & Nardell, 1998).
On page 43
Fennelly KP, Nardell EA. The relative efficacy of respirators and room ventilation in preventing occupational tuberculosis. Infection Control and Hospital Epidemiology, 1998, 19(10):754–759.
American Journal of Respiratory and Critical Care Medicine (American Thoracic Society)
Kevin P. Fennelly et al. 2004
There have been several studies on the number and size of droplets of saliva and other secretions from respiratory activities (Jennison, 1942; Duguid, 1945; Hamburger & Roberston, 1946; Loudon & Roberts, 1967; Papineni & Rosenthal, 1997; Fennelly et al., 2004) and excellent reviews have been written (Nicas, Nazaroff & Hubbard, 2005; Morawska, 2006).
There is also a great individual variability (Papineni & Rosenthal, 1997; Fennelly et al., 2004).
Fennelly KP et al. Cough-generated aerosols of Mycobacterium tuberculosis: a new method to study infectiousness. American Journal of Respiratory and Critical Care Medicine, 2004, 169(5):604–609.
Infection Control and Hospital Epidemiology (JSTOR)
Victoria J. Fraser et al. 1993
Other problems with mechanical ventilation include the loss of negative pressure differential in isolation rooms due to the opening of the doors; clogged filters; and adjacent, negatively pressurized spaces (Fraser et al., 1993; Dahl et al., 1996; Sutton et al., 1998; Pavelchak et al., 2001; Rice, Streifel & Vesley, 2001).
On page 40
Fraser VJ et al. Evaluation of rooms with negative pressure ventilation used for respiratory isolation in seven midwestern hospitals. Infection Control and Hospital Epidemiology, 1993, 14(11):623–628.
American Journal of Infection Control (Elsevier BV)
THEHOSPITALINFECTIONCONTROLPRACTIC et al. 1996
Gardner J. Centers for Disease Control: guideline for isolation precautions in hospitals. American Journal of Infection Control, 1996, 24:2–52.
Infection Control and Hospital Epidemiology (JSTOR)
Julie Louise Gerberding 1993
When using isolation precautions, three levels of controls must be considered (Gerberding, 1993).
On page 29
Gerberding JL. Occupational infectious diseases or infectious occupational diseases? Bridging the views on tuberculosis controls. Infection Control and Hospital Epidemiology, 1993, 14:686–687.
The American Journal of Medicine (Elsevier BV)
Morton Hamburger et al. 1948
Hamburger M, Roberston OH. Expulsion of group A hemolytic streptococci in droplets and droplet nuclei by sneezing, coughing, and talking. American Journal of Medicine, 1946, 4:690–701.
Applied Occupational and Environmental Hygiene (Informa UK Limited)
Charles S. Hayden et al. 1998
Entrainment of air into neighbouring airspaces may occur during the most innocuous daily activities; for example, as a result of people walking, or the opening of a door between a room and the adjacent corridor or space (Hayden et al., 1998; Edge, Paterson & Settles, 2005; Tang et al., 2005, 2006).
Hayden CS et al. Air volume migration from negative pressure isolation rooms during entry/exit. Applied Occupational and Environmental Hygiene, 1998, 13(7):518– 527.
International Journal of Ventilation (Informa UK Limited)
Per Heiselberg et al. 2002
It uses mechanical ventilation when the natural ventilation flow rate is too low (Heiselberg & Bjørn, 2002).
On page 34
Heiselberg P, Bjørn E. Impact of open windows on room air-flow and thermal comfort. International Journal of Ventilation, 2002, 1(2):91–100.
Journal of Infectious Diseases (Oxford University Press (OUP))
M. D. Hutton et al. 1990
The diseases that showed a possible association between transmission among humans and ventilation were chickenpox (Gustafson et al., 1982), measles (Bloch et al., 1985), smallpox (Wehrle et al., 1970) and pulmonary tuberculosis (TB) (Hutton et al., 1990; Calder et al., 1991; Menzies et al., 2000).
On page 44
To help prevent airborne infections, adequate ventilation in health-care facilities in all patient-care areas is necessary (Gustafson et al., 1982; Bloch et al., 1985; Hutton et al. 1990; Calder et al. 1991).
On page 47
When designing naturally ventilated health-care facilities, overall airflow should bring the air from the agent sources to areas where there is sufficient dilution, and preferably to the outdoors (Gustafson et al., 1982; Bloch et al., 1985; Hutton et al. 1990; Calder et al. 1991).
On page 48
Population: Health-care settings Intervention: Ventilation Factor Decision Explanation Quality of evidence Moderate There is moderate evidence available to suggest that insufficient ventilation is associated with an increased risk of infection (Gustafson et al., 1982; Bloch et al., 1985; Hutton et al., 1990; Calder et al., 1991).
On page 99
Population: Health-care settings Intervention: Airflow control in natural ventilation Factor Decision Explanation Quality of evidence Low There is moderate evidence available to suggest that incorrect airflow direction is associated with an increased risk of infection (Gustafson et al., 1982; Bloch et al., 1985; Hutton et al., 1990; Calder et al., 1991).
Recommendation 1 was based mainly on the studies of Gustafson et al. (1982) (chickenpox), Bloch et al. (1985) (measles), Hutton et al. (1990) (TB) and Calder et al. (1991) (TB).
On page 49
Hutton MD et al. Nosocomial transmission of tuberculosis associated with a draining abscess. Journal of Infectious Diseases, 1990, 161(2):286–295.
Clinical Infectious Diseases (Oxford University Press (OUP))
Kerrianne N. Huynh et al. 2008
Detection of pathogens in room air and buildings may suggest a possible, indirect association between ventilation and disease transmission (Artenstein et al., 1967; Sawyer et al., 1994; Aintablian, Walpita & Sawyer, 1998; Mastorides et al., 1999; Suzuki et al., 2002, 2003; Booth et al., 2005; Chen & Li, 2008; Huynh et al., 2008).
On page 43
Huynh KN et al. A new method for sampling and detection of exhaled respiratory virus aerosols. Clinical Infectious Diseases, 2008, 46(1):93–95.
American Journal of Infection Control (Elsevier BV)
Margaret Ip et al. 2007
Ip M et al. Air-flow and droplet spreading around oxygen masks: a simulation model for infection control research. American Journal of Infection Control, 2007, 35(10):684–689.
New England Journal of Medicine (New England Journal of Medicine (NEJM/MMS))
Bruce S. Klein et al. 1989
Although there is no single study showing the effectiveness of isolation, there are many reports documenting the efficacy of the various components of isolation, including use of private rooms (Anderson et al., 1985), and protective equipments such as masks, gloves and gowns (Klein, Perloff & Maki, 1989; Maki, 1994; Maloney et al., 1995).
On page 29
Klein BS, Perloff WH, Maki DG. Reduction of nosocomial infection during pediatric intensive care by protective isolation. New England Journal of Medicine, 1989, 320(26):1714–1721.
Selecting low-emission interior materials A comprehensive understanding of air pollutant emissions from interior building materials has developed over the years (Levin, 1989; Li & Niu, 2007).
On page 64
Li F, Niu JL. Control of volatile organic compounds indoors — development of an integrated mass-transfer-based model and its application. Atmospheric Environment, 2007, 41(11):2344–2354.
Indoor and Built Environment (SAGE Publications)
Yuguo Li et al. 2007
Li Y et al. An evaluation of the ventilation performance of new SARS isolation wards in nine hospitals in Hong Kong. Indoor and Built Environment, 2007, 16(5):400– 410.
Although there is no single study showing the effectiveness of isolation, there are many reports documenting the efficacy of the various components of isolation, including use of private rooms (Anderson et al., 1985), and protective equipments such as masks, gloves and gowns (Klein, Perloff & Maki, 1989; Maki, 1994; Maloney et al., 1995).
On page 29
Maki DG. Yes, Virginia, aseptic technique is very important: maximal barrier precautions during insertion reduce the risk of central venous catheter-related bacteremia. Infection Control and Hospital Epidemiology, 1994, 15(4 Pt 1):227–230.
Although there is no single study showing the effectiveness of isolation, there are many reports documenting the efficacy of the various components of isolation, including use of private rooms (Anderson et al., 1985), and protective equipments such as masks, gloves and gowns (Klein, Perloff & Maki, 1989; Maki, 1994; Maloney et al., 1995).
On page 29
Maloney SA et al. Efficacy of control measures in preventing nosocomial transmission of multidrug-resistant tuberculosis to patients and health care workers. Annals of Internal Medicine, 1995, 122(2):90–95.
Detection of pathogens in room air and buildings may suggest a possible, indirect association between ventilation and disease transmission (Artenstein et al., 1967; Sawyer et al., 1994; Aintablian, Walpita & Sawyer, 1998; Mastorides et al., 1999; Suzuki et al., 2002, 2003; Booth et al., 2005; Chen & Li, 2008; Huynh et al., 2008).
On page 43
Mastorides SM et al. The detection of airborne Mycobacterium tuberculosis using micropore membrane air sampling and polymerase chain reaction. Chest, 1999, 115(1):19–25.
Annals of Internal Medicine (American College of Physicians)
Dick Menzies 2000
The diseases that showed a possible association between transmission among humans and ventilation were chickenpox (Gustafson et al., 1982), measles (Bloch et al., 1985), smallpox (Wehrle et al., 1970) and pulmonary tuberculosis (TB) (Hutton et al., 1990; Calder et al., 1991; Menzies et al., 2000).
On page 44
Recommendation 2 was based mainly on the studies of Menzies et al. (2000) and Bloch et al. (1985), which provided evidence of an association between low ventilation rate (lower than 2 ACH) and the spread of TB (Menzies et al., 2000) and measles (Bloch et al., 1985).
On page 49
Feasibility Overall ranking Moderate (benefits sometimes outweigh disadvantages) May be low and high Conditional to country settings CONDITIONAL RECOMMENDATION There is no direct evidence available to suggest the direct impact of natural ventilation on disease transmission, though there is strong engineering evidence that natural ventilation can achieve a very high ventilation rate and it is suggested that a high ventilation rate can reduce airborne infection (Menzies et al., 2000).
In line with this assumption, Menzies et al. (2000) found that the tuberculin conversion among clinical personnel was significantly more rapid and frequent among those working in average ventilation lower than 2 ACH.
On page 45
Menzies D et al. Hospital ventilation and risk for tuberculous infection in Canadian health care workers. Annals of Internal Medicine, 2000, 133(10):779–789.
and excellent reviews have been written (Nicas, Nazaroff & Hubbard, 2005; Morawska, 2006).
Morawska L. Droplet fate in indoor environments, or can we prevent the spread of infection? Indoor Air, 2006, 16(5):335–347.
American Review of Respiratory Disease (American Thoracic Society)
Edward A. Nardell et al. 1991
The Wells–Riley equation (Riley, Murphy & Riley, 1978) was used to evaluate the effect of ventilation, filtration and other physical processes on transmission through droplet nuclei (Nardell et al., 1991; Fennelly & Nardell, 1998).
On page 43
Nardell EA et al. Airborne infection: theoretical limits of protection achievable by building ventilation. American Review of Respiratory Diseases, 1991, 144(2):302–306.
Journal of Occupational and Environmental Hygiene (Informa UK Limited)
Mark Nicas et al. 2005
and excellent reviews have been written (Nicas, Nazaroff & Hubbard, 2005; Morawska, 2006).
Nicas M, Nazaroff WW, Hubbard A. Toward understanding the risk of secondary airborne infection: emission of respirable pathogens. Journal of Occupational and Environmental Hygiene, 2005, 2(3):143–154.
HKIE Transactions (The Hong Kong Institution of Engineers)
J L Niu 2001
For example, in buildings with a heavy structure and that use natural ventilation, a sudden change of weather with warm, moist ambient air may induce condensation when the surface temperature is lower than the dew-point temperature of the moist incoming air (Niu, 2001).
On page 64
Niu JL. Technology options for humidity control for hotels in south-eastern China climate. HKIE Transactions, 2001, 8(2):20–24.
Journal of Aerosol Medicine (Mary Ann Liebert Inc)
RAO S. PAPINENI et al. 1997
There have been several studies on the number and size of droplets of saliva and other secretions from respiratory activities (Jennison, 1942; Duguid, 1945; Hamburger & Roberston, 1946; Loudon & Roberts, 1967; Papineni & Rosenthal, 1997; Fennelly et al., 2004) and excellent reviews have been written (Nicas, Nazaroff & Hubbard, 2005; Morawska, 2006).
There is also a great individual variability (Papineni & Rosenthal, 1997; Fennelly et al., 2004).
Papineni RS, Rosenthal FS. The size distribution of droplets in the exhaled breath of healthy human subjects. Journal of Aerosol Medicine, 1997, 10(2):105–116.
Infection Control & Hospital Epidemiology (Cambridge University Press (CUP))
Nicholas Pavelchak et al. 2000
For example, Pavelchak et al. (2000) evaluated 140 designated airborne infection isolation rooms in 38 facilities during 1992 to 1998 and found that unwanted directional airflow out of the patient room was observed in 38% of the facilities.
On page 39
Pavelchak N et al. Identification of factors that disrupt negative air pressurization of respiratory isolation rooms. Infection Control and Hospital Epidemiology, 2000, 21(3):191–195.
Infection Control & Hospital Epidemiology (Cambridge University Press (CUP))
Nicholas Pavelchak et al. 2001
Other problems with mechanical ventilation include the loss of negative pressure differential in isolation rooms due to the opening of the doors; clogged filters; and adjacent, negatively pressurized spaces (Fraser et al., 1993; Dahl et al., 1996; Sutton et al., 1998; Pavelchak et al., 2001; Rice, Streifel & Vesley, 2001).
On page 40
Pavelchak N et al. Negative-pressure monitoring of tuberculosis isolation rooms within New York State hospitals. Infection Control and Hospital Epidemiology, 2001, 22(8):518–519.
Patients lying in bed, breathing or sleeping, may produce exhaled airflows that can reach the airspace of a patient in the neighbouring bed, and even further in the presence of certain types of ventilation systems (see below) (Qian et al., 2006).
Qian H et al. Dispersion of exhaled droplet nuclei in a two-bed hospital ward with three different ventilation systems. Indoor Air, 2006, 16(2):111–128.
Infection Control & Hospital Epidemiology (Cambridge University Press (CUP))
Nancy Rice et al. 2001
Other problems with mechanical ventilation include the loss of negative pressure differential in isolation rooms due to the opening of the doors; clogged filters; and adjacent, negatively pressurized spaces (Fraser et al., 1993; Dahl et al., 1996; Sutton et al., 1998; Pavelchak et al., 2001; Rice, Streifel & Vesley, 2001).
On page 40
Rice N, Streifel A, Vesley D. An evaluation of hospital special-ventilation-room pressures. Infection Control and Hospital Epidemiology, 2001, 22(1):19–23.
American Journal of Epidemiology (Oxford University Press (OUP))
E. C. RILEY et al. 1978
The Wells–Riley equation (Riley, Murphy & Riley, 1978) was used to evaluate the effect of ventilation, filtration and other physical processes on transmission through droplet nuclei (Nardell et al., 1991; Fennelly & Nardell, 1998).
On page 43
Riley EC, Murphy G, Riley RL. Airborne spread of measles in a suburban elementary school. American Journal of Epidemiology, 1978, 107(5):421–432.
New England Journal of Medicine (New England Journal of Medicine (NEJM/MMS))
Chad J. Roy et al. 2004
The mechanism of this transmission is described as an opportunistic airborne transmission (Roy & Milton, 2004), and high-risk procedures may increase the potential of generating droplet nuclei because of the mechanical force of the procedure (Ip et al., 2007).
On page 31
Roy CJ, Milton DK. Airborne transmission of communicable infection — the elusive pathway. New England Journal of Medicine, 2004, 350(17):1710–1712.
Journal of Infectious Diseases (Oxford University Press (OUP))
M. H. Sawyer et al. 1994
Detection of pathogens in room air and buildings may suggest a possible, indirect association between ventilation and disease transmission (Artenstein et al., 1967; Sawyer et al., 1994; Aintablian, Walpita & Sawyer, 1998; Mastorides et al., 1999; Suzuki et al., 2002, 2003; Booth et al., 2005; Chen & Li, 2008; Huynh et al., 2008).
On page 43
Sawyer MH et al. Detection of Varicella-zoster virus DNA in air samples from hospital rooms. Journal of Infectious Diseases, 1994, 169(1):91–94.
Siegel JD et al. 2007 guideline for isolation precautions: preventing transmission of infectious agents in healthcare settings. Public Health Service, US Department of Health and Human Services, Centers for Disease Control and Prevention, 2007 (http://www.cdc.gov/ncidod/dhqp/pdf/guidelines/Isolation2007.pdf).
Current Opinion in Biotechnology (Elsevier BV)
Linda D Stetzenbach et al. 2004
In contrast, the term droplet nuclei refers to droplets ≤5 μm in diameter that can remain suspended in air for significant periods of time, allowing them to be transmitted over distances >1 m (Stetzenbach, Buttner & Cruz, 2004; Wong & Leung, 2004).
Stetzenbach LD, Buttner MP, Cruz P. Detection and enumeration of airborne biocontaminants. Current Opinion in Biotechnology, 2004, 15(3):170–174.
Other problems with mechanical ventilation include the loss of negative pressure differential in isolation rooms due to the opening of the doors; clogged filters; and adjacent, negatively pressurized spaces (Fraser et al., 1993; Dahl et al., 1996; Sutton et al., 1998; Pavelchak et al., 2001; Rice, Streifel & Vesley, 2001).
On page 40
Sutton PM et al. Evaluating the control of tuberculosis among healthcare workers: adherence to CDC guidelines of three urban hospitals in California. Infection Control and Hospital Epidemiology, 1998, 19(7):487–493.
Detection of pathogens in room air and buildings may suggest a possible, indirect association between ventilation and disease transmission (Artenstein et al., 1967; Sawyer et al., 1994; Aintablian, Walpita & Sawyer, 1998; Mastorides et al., 1999; Suzuki et al., 2002, 2003; Booth et al., 2005; Chen & Li, 2008; Huynh et al., 2008).
On page 43
Suzuki K et al. Detection of Varicella-zoster virus DNA in throat swabs of patients with herpes zoster and on air purifier filters. Journal of Medical Virology, 2002, 66(4):567–570.
Suzuki K et al. Spread of Varicella-zoster virus DNA to the environment from Varicella patients who were treated with oral acyclovir. Pediatrics International, 2003, 45(4):458–460.
Entrainment of air into neighbouring airspaces may occur during the most innocuous daily activities; for example, as a result of people walking, or the opening of a door between a room and the adjacent corridor or space (Hayden et al., 1998; Edge, Paterson & Settles, 2005; Tang et al., 2005, 2006).
In addition, the air temperature (and therefore air density) differences across an open doorway will also cause air exchange to occur between the two areas, providing a second mechanism to allow air into other areas (Tang et al., 2005, 2006) (see Figure C.3).
(B) Demonstration of how opening a door may transport air from inside an isolation room to the outside, during the door-opening motion itself (Tang et al., 2005).
(C) Demonstration of how an open door can allow air of different temperatures and densities to mix and exchange (Tang et al. 2005).
Tang JW et al. Door-opening motion can potentially lead to a transient breakdown in negative-pressure isolation conditions: the importance of vorticity and buoyancy air-flows. Journal of Hospital Infection, 2005, 61(4):283–286.
Other studies suggest slightly different definitions, with ranges for “large” droplets, “small” droplets and droplet nuclei being >60 μm in diameter, ≤60 μm in diameter and <10 μm in diameter, respectively (Tang et al., 2006; Xie et al., 2007).
Published data have suggested that sneezing may produce as many as 40 000 droplets between 0.5–12 μm in diameter (Cole & Cook, 1998; Tang et al., 2006) that may be expelled at speeds up to 100 m/s (Wells, 1955; Cole & Cook, 1998), whereas coughing may produce up to 3000 droplet nuclei, about the same number as talking for five minutes (Cole & Cook, 1998; Fitzgerald & Haas, 2005; Tang et al., 2006).
(A) (B) (C) (A) Demonstration of how a walking person may entrain air into their wake (Tang et al., 2006).
Tang JW et al. Factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises. Journal of Hospital Infection, 2006, 64(2):100–114.
Wehrle PF et al. An airborne outbreak of smallpox in a German hospital and its significance with respect to other recent outbreaks in Europe. Bulletin of the World Health Organization, 1970, 43:669–679.
Managing ambient air pollution With the high air-change rate of untreated outdoor air, indoor air quality will be more affected by the ambient air pollution (Weschler & Shields, 2000; Ghiaus et al., 2005).
On page 64
Weschler CJ, Shields HC. The influence of ventilation on reactions among indoor pollutants: modelling and experimental observations. Indoor Air, 2000, 10(2):92– 100.
WHO. Infection prevention and control of epidemic- and pandemic-prone acute respiratory diseases in health care — WHO interim guidelines. Geneva, World Health Organization, 2007.
PLoS Medicine (Public Library of Science (PLoS))
Peter Wilson 2007
Wilson P. Is natural ventilation a useful tool to prevent the air borne spread of TB? PLoS Medicine, 2007, 4(2):e77.
The Journal of Bone & Joint Surgery (Ovid Technologies (Wolters Kluwer Health))
Kwok Chuen Wong et al. 2004
In contrast, the term droplet nuclei refers to droplets ≤5 μm in diameter that can remain suspended in air for significant periods of time, allowing them to be transmitted over distances >1 m (Stetzenbach, Buttner & Cruz, 2004; Wong & Leung, 2004).
Wong KC, Leung KS. Transmission and prevention of occupational infections in orthopaedic surgeons. Journal of Bone and Joint Surgery America, 2004, 86-A (5):1065–1076.
Other studies suggest slightly different definitions, with ranges for “large” droplets, “small” droplets and droplet nuclei being >60 μm in diameter, ≤60 μm in diameter and <10 μm in diameter, respectively (Tang et al., 2006; Xie et al., 2007).
Xie X et al. How far droplets can move in indoor environments — revisiting the Wells evaporation-falling curve. Indoor Air, 2007, 17(3):211–225.
Building Services Engineering Research and Technology (SAGE Publications)
Zhang Huan et al. 2000
This strategy also has a relatively low cost, compared with a full air-conditioning system (Zhang et al., 2000).
On page 63
Zhang H et al. Enhanced performance of air-cooled chillers using evaporative cooling. Building Services Engineering Research and Technology, 2000, 21(4):213–217.
Infection Control (Cambridge University Press (CUP))
John D. Anderson et al. 1985
Although there is no single study showing the effectiveness of isolation, there are many reports documenting the efficacy of the various components of isolation, including use of private rooms (Anderson et al., 1985), and protective equipments such as masks, gloves and gowns (Klein, Perloff & Maki, 1989; Maki, 1994; Maloney et al., 1995).
On page 29
Anderson JD et al. Lack of nosocomial spread of Varicella in a pediatric hospital with negative pressure ventilated patient rooms. Infection Control, 1985, 6(3):120–121.
Basu S et al. Prevention of nosocomial transmission of extensively drug-resistant tuberculosis in rural South African district hospitals: an epidemiological modelling study. Lancet, 2007, 370(9597):1500–1507.
JAMA: The Journal of the American Medical Association (American Medical Association (AMA))
J. F. Brundage 1988
Brundage JF et al. Building-associated risk of febrile acute respiratory diseases in army trainees. JAMA, 1988, 259(14):2108–2112.
Scandinavian Journal of Infectious Diseases (Informa UK Limited)
HÅKan Cars et al. 1992
Cars H, Petersson C, Hakansson A. Infectious-diseases and day-care-center environment. Scandinavian Journal of Infectious Diseases, 1992, 24(4):525–528.
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To help prevent airborne infections, adequate ventilation in health-care facilities in all patient-care areas is necessary (Gustafson et al., 1982; Bloch et al., 1985; Hutton et al. 1990; Calder et al. 1991).
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When designing naturally ventilated health-care facilities, overall airflow should bring the air from the agent sources to areas where there is sufficient dilution, and preferably to the outdoors (Gustafson et al., 1982; Bloch et al., 1985; Hutton et al. 1990; Calder et al. 1991).
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Population: Health-care settings Intervention: Ventilation Factor Decision Explanation Quality of evidence Moderate There is moderate evidence available to suggest that insufficient ventilation is associated with an increased risk of infection (Gustafson et al., 1982; Bloch et al., 1985; Hutton et al., 1990; Calder et al., 1991).
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Population: Health-care settings Intervention: Airflow control in natural ventilation Factor Decision Explanation Quality of evidence Low There is moderate evidence available to suggest that incorrect airflow direction is associated with an increased risk of infection (Gustafson et al., 1982; Bloch et al., 1985; Hutton et al., 1990; Calder et al., 1991).
Recommendation 1 was based mainly on the studies of Gustafson et al. (1982) (chickenpox), Bloch et al. (1985) (measles), Hutton et al. (1990) (TB) and Calder et al. (1991) (TB).
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The diseases that showed a possible association between transmission among humans and ventilation were chickenpox (Gustafson et al., 1982), measles (Bloch et al., 1985), smallpox (Wehrle et al., 1970) and pulmonary tuberculosis (TB) (Hutton et al., 1990; Calder et al., 1991; Menzies et al., 2000).
On page 44
Recommendation 2 was based mainly on the studies of Menzies et al. (2000) and Bloch et al. (1985), which provided evidence of an association between low ventilation rate (lower than 2 ACH) and the spread of TB (Menzies et al., 2000) and measles (Bloch et al., 1985).
On page 49
Feasibility Overall ranking Moderate (benefits sometimes outweigh disadvantages) May be low and high Conditional to country settings CONDITIONAL RECOMMENDATION There is no direct evidence available to suggest the direct impact of natural ventilation on disease transmission, though there is strong engineering evidence that natural ventilation can achieve a very high ventilation rate and it is suggested that a high ventilation rate can reduce airborne infection (Menzies et al., 2000).
In line with this assumption, Menzies et al. (2000) found that the tuberculin conversion among clinical personnel was significantly more rapid and frequent among those working in average ventilation lower than 2 ACH.
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Entrainment of air into neighbouring airspaces may occur during the most innocuous daily activities; for example, as a result of people walking, or the opening of a door between a room and the adjacent corridor or space (Hayden et al., 1998; Edge, Paterson & Settles, 2005; Tang et al., 2005, 2006).
In addition, the air temperature (and therefore air density) differences across an open doorway will also cause air exchange to occur between the two areas, providing a second mechanism to allow air into other areas (Tang et al., 2005, 2006) (see Figure C.3).
(B) Demonstration of how opening a door may transport air from inside an isolation room to the outside, during the door-opening motion itself (Tang et al., 2005).
(C) Demonstration of how an open door can allow air of different temperatures and densities to mix and exchange (Tang et al. 2005).
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