Possible Role of Aerosol Transmission in a Hospital Outbreak of Influenza

Wong, Billy; Lee, Nelson; Li, Yuguo; Chan, Paul K.S.; Qiu, Hong; Luo, Zhiwen; Lai, Robin Kit-Ho; Ngai, Karry L. K.; Hui, David S.; Choi, Kin Wing; Yu, Ignatius Tak Sun

doi:10.1086/656743

Cited by 107 publications

(109 citation statements)

References 37 publications

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“…(11) Two air sampling studies have shown that respirable particles containing influenza virus RNA can be found throughout health care facilities, (12,13) and a recent hospital study suggested that small aerosol particles from an influenza patient were blown by an air purifier toward other patients in a hospital ward, leading to additional infections much farther away. (14) Thus, many questions remain as to the risk of exposure to diseases like influenza and the circumstances under which respiratory protection is needed.…”

Section: Introductionmentioning

confidence: 99%

Dispersion and Exposure to a Cough-Generated Aerosol in a Simulated Medical Examination Room

Lindsley

King

Thewlis

et al. 2012

Journal of Occupational and Environmental Hygiene

102

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Few studies have quantified the dispersion of potentially infectious bioaerosols produced by patients in the health care environment and the exposure of health care workers to these particles. Controlled studies are needed to assess the spread of bioaerosols and the efficacy of different types of respiratory personal protective equipment (PPE) in preventing airborne disease transmission. An environmental chamber was equipped to simulate a patient coughing aerosol particles into a medical examination room, and a health care worker breathing while exposed to these particles. The system has three main parts: (1) a coughing simulator that expels an aerosol-laden cough through a head form; (2) a breathing simulator with a second head form that can be fitted with respiratory PPE; and (3) aerosol particle counters to measure concentrations inside and outside the PPE and at locations throughout the room. Dispersion of aerosol particles with optical diameters from 0.3 to 7.5 μm was evaluated along with the influence of breathing rate, room ventilation, and the locations of the coughing and breathing simulators. Penetration of cough aerosol particles through nine models of surgical masks and respirators placed on the breathing simulator was measured at 32 and 85 L/min flow rates and compared with the results from a standard filter tester. Results show that cough-generated aerosol particles spread rapidly throughout the room, and that within 5 min, a worker anywhere in the room would be exposed to potentially hazardous aerosols. Aerosol exposure is highest with no personal protective equipment, followed by surgical masks, and the least exposure is seen with N95 FFRs. These differences are seen regardless of breathing rate and relative position of the coughing and breathing simulators. These results provide a better understanding of the exposure of workers to cough aerosols from patients and of the relative efficacy of different types of respiratory PPE, and they will assist investigators in providing research-based recommendations for effective respiratory protection strategies in health care settings.

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Section: Introductionmentioning

confidence: 99%

Dispersion and Exposure to a Cough-Generated Aerosol in a Simulated Medical Examination Room

Lindsley

King

Thewlis

et al. 2012

Journal of Occupational and Environmental Hygiene

102

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“…Wong and colleagues used a computational fluid dynamics model to study the spread of an influenza outbreak in a hospital setting [39]. Concentrations of hypothetical virus-laden particles from modelled air distributions correlated closely with locations of infected patients.…”

Section: Comparing Results With Established Factsmentioning

confidence: 99%

Spatial methods for infectious disease outbreak investigations: systematic literature review

et al. 2015

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Investigations of infectious disease outbreaks are conventionally framed in terms of person, time and place. Although geographic information systems have increased the range of tools available, spatial analyses are used relatively infrequently. We conducted a systematic review of published reports of outbreak investigations worldwide to estimate the prevalence of spatial methods, describe the techniques applied and explore their utility. We identified 80 reports using spatial methods published between 1979 and 2013, ca 0.4% of the total number of published outbreaks. Environmental or waterborne infections were the most commonly investigated, and most reports were from the United Kingdom. A range of techniques were used, including simple dot maps, cluster analyses and modelling approaches. Spatial tools were usefully applied throughout investigations, from initial confirmation of the outbreak to describing and analysing cases and communicating findings. They provided valuable insights that led to public health actions, but there is scope for much wider implementation and development of new methods.

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“…This could be done through a ventilation network model, such as CON-TAM, or one of the many commercially available building simulation tools or even modeling a ward zone within a CFD simulation to assess the likely spatial distribution of infectious material in a real situation. In the case of CFD approaches, steady-state airflow models without the movement of people have been shown to have reasonable correlation with infection cases seen in ward (Wong et al 2010) and building (Yu et al 2004) outbreaks.…”

Section: Zonal Modeling Approachmentioning

confidence: 97%

Modeling infection risk and energy use of upper-room Ultraviolet Germicidal Irradiation systems in multi-room environments

Noakes

Khan

Gilkeson

2015

Science and Technology for the Built Environment

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The effectiveness of ultraviolet irradiation at inactivating airborne pathogens is well proven, and the technology is also commonly promoted as an energy-efficient way of reducing infection risk in comparison to increasing ventilation. However, determining how and where to apply upper-room Ultraviolet Germicidal Irradiation devices for the greatest benefit is still poorly understood. This article links multi-zone infection risk models with energy calculations to assess the potential impact of a Ultraviolet Germicidal Irradiation installation across a series of inter-connected spaces, such as a hospital ward. A first-order decay model of ultraviolet inactivation is coupled with a room air model to simulate patient room and whole-ward level disinfection under different mixing and ultraviolet field conditions. Steady-state computation of quanta-concentrations is applied to the Wells-Riley equation to predict likely infection rates. Simulation of a hypothetical ward demonstrates the relative influence of different design factors for susceptible patients co-located with an infectious source or in nearby rooms. In each case, energy requirements are calculated and compared to achieving the same level of infection risk through improved ventilation. Ultraviolet devices are seen to be most effective where they are located close to the infectious source; however, when the location of the infectious source is not known, locating devices in patient rooms is likely to be more effective than installing them in connecting corridor or communal zones. Results show an ultraviolet system may be an energy-efficient solution to controlling airborne infection, particularly in semi-open hospital environments, and considering the whole ward rather than just a single room at the design stage is likely to lead to a more robust solution.

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Possible Role of Aerosol Transmission in a Hospital Outbreak of Influenza

Abstract: Our findings suggest a possible role of aerosol transmission of influenza in an acute ward setting. Source and engineering controls, such as avoiding aerosol generation and improving ventilation design, may warrant consideration to prevent nosocomial outbreaks.

Cited by 107 publications

References 37 publications

Dispersion and Exposure to a Cough-Generated Aerosol in a Simulated Medical Examination Room

Dispersion and Exposure to a Cough-Generated Aerosol in a Simulated Medical Examination Room

Spatial methods for infectious disease outbreak investigations: systematic literature review

Modeling infection risk and energy use of upper-room Ultraviolet Germicidal Irradiation systems in multi-room environments

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