Figure - available from: International Journal of Environmental Research and Public Health (IJERPH)
This content is subject to copyright.
Source publication
In this study, the results of an airflow investigation conducted on 7 June 2015 as part of a series of epidemiologic investigations at Pyeongtaek St. Mary’s Hospital, South Korea, were investigated. The study involved 38 individuals who were infected directly and indirectly with Middle East Respiratory Syndrome (MERS), by a super-spreader patient....
Similar publications
Middle East respiratory syndrome (MERS) is known to be transmitted through close contact. However, epidemiological surveys of MERS in Korea indicated that some secondary patients were infected without close contact. Therefore, the possibility of other transmission routes must be identified. In this study, the possibility of MERS spreading through a...
Citations
... Sung et al. [23] carried out the tracer experiments for the 38 individuals infected in the MERS outbreak. As a result of the study carried out in a hospital in South Korea, it was indicated that precautions are essential in such cases and that airflow is a possible route of transmission. ...
The novel coronavirus (SARS-CoV-2) outbreak has spread worldwide, and the World Health Organization (WHO) declared a global pandemic in March 2020. The transmission mechanism of SARS-CoV-2 in indoor environments has begun to be investigated in all aspects. In this regard, many numerical studies on social distancing and the protection of surgical masks against infection risk have neglected the evaporation of the particles. Meanwhile, a 1.83 m (6 feet) social distancing rule has been recommended to reduce the infection risk. However, it should be noted that most of the studies were conducted in static air conditions. Air movement in indoor environments is chaotic, and it is not easy to track all droplets in a ventilated room experimentally. Computational Fluid Dynamics (CFD) enables the tracking of all particles in a ventilated environment. This study numerically investigated the airborne transmission of infectious droplets in a hospital examination room cooled by a split-type air conditioner with the CFD method. Different inlet velocities (1, 2, 3 m/s) were considered and investigated separately. Besides, the hospital examination room is a model of one of the Bursa Uludag University Hospital examination rooms. The patient, doctor, and some furniture are modeled in the room. Particle diameters considered ranged from 2 to 2000 μm. The evaporation of the droplets is not neglected, and the predictions of particle tracks are shown. As a result, locations with a high infection risk were identified, and the findings that could guide the design/redesign of the hospital examination rooms were evaluated.
... The experimental results could be the empirical evidence for identifying the transmission pathways and verifying the infection timeline. Sung et al. 104 confirmed experimentally that indoor airflow made the long-distance spread of the Middle East respiratory syndrome (MERS) infection possible. The tracer gas's bioaerosols surrogate dispersion pattern matched perfectly with the epidemiologic observations, indicating the infection routes via ventilation in the hospital. ...
... The technique can be easily implemented in large areas in real hospitals with minimal disturbance to regular operation, making it ideal for outbreak investigation (e.g. Sung et al. 104 and Huang et al.). 106 This technique was also used in mock-ups to investigate respiratory contaminants' dispersion influenced by various factors, including building ventilation. ...
... Experimental studies that employed tracer gases often had a limited number of sampling points, typically less than nine, 72,84,113 even in studies conducted throughout an entire hospital floor. 104 This sampling limitation can be attributed to the high cost of tracer gas sampling instruments. 137 Similarly, in aerosol experiments, the number of sampling points was often limited, 78,82,92,96 with the highest reported number of sampling points being 13. ...
Experimental studies can provide understanding, knowledge and real-case empirical evidence on the effects of building ventilation and environmental factors on airborne transmission in hospitals. Information obtained from existing studies gives insight into formulating engineering solutions and management practices to combat nosocomial airborne infections. A systemic review was conducted to summarize the experimental methods, research interests, useful results and limitations. With a steady but slow trend of increasing interest, experimental studies have been focusing mainly on the effects of ventilation systems, strategies and configurations on airborne transmission. The dispersion of bioaerosols under the combined effects of environmental factors, emission scenarios and human movement was investigated. Localized ventilation, air purifiers and disinfection technologies were also examined. The experimental techniques and some useful insights on optimal ventilation strategies and management practices were summarized and highlighted. Limitations of the empirical studies included sampling difficulties, limited scale and a number of testing scenarios, uncontrolled/unconsidered influencing factors and the media for experimentations. Using IoT-based sampling devices for experiments and real-time monitoring of bioaerosols or their surrogates, field surveys on a case-by-case basis in hospitals and interdisciplinary studies and collaborations could help overcome the research challenges and provide practical and effective solutions to minimize airborne transmission in hospitals.
... While some researchers used a tracer gas to assess the efficiency of various ventilation systems in removing contaminants from the breathing zone of a susceptible patient [13,14], some other employed it to assess the dispersion of exhaled pollutants and evaluate airborne infection risk. Sung et al. [15] identified the spatial distribution of a tracer gas at six sampling points in a hospital to examine the possibility of the spread of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) through indoor airflow. Bolashikov et al. [16] measured the carbon dioxide levels in a patient room at three different locations away from a simulated coughing patient to evaluate the exposure of HCWs and occupants to coughed airborne pathogens. ...
... In the position paper by Ai et al. [26], based on a review of studies that demonstrated tracer gas could accurately simulate the movement of small particles with diameters of 3-5 μm, and the fact that the aerodynamics of fine droplet nuclei with infectious pathogens are more similar to those of a gas, the authors argued that tracer gas simulation is a suitable surrogate for studying airborne transmission in the built environment as it is less complex and requires less user expertise. Tracer gas therefore can be considered a good and practical indication of the movement of bioaerosols and is widely adopted in current experimental studies on long-range airborne transmission such as Sung et al. [15] and Huang et al. [27]. It is noteworthy that the use of tracer gases may not adequately represent the deposition and resuspension of bioaerosols on surfaces, and the viability, and infectivity of bioaerosols can be influenced by elements such as temperature, humidity, and airflows, which may not be fully reflected by tracer gases [26]. ...
... According to the weather data in Pyeongtaek between 15 and 17 May 2015, when the index patient was admitted, west and west-southwest winds at a temperature of 17.8 °C were prevalent, and the wind velocity at 10 m above ground was 2.6 m/s for the west wind and 2.62 m/s for the west-southwest wind [21]. And the average relative humidity was 67.2%. ...
... The roughness of the earth's surface, the α value, was set to 0.22 (for regions where houses with a height of 3.5 m are concentrated or regions where middle-class buildings are scattered) according to the Korea Building Code [22]. According to the weather data in Pyeongtaek between 15 and 17 May 2015, when the index patient was admitted, west and west-southwest winds at a temperature of 17.8 • C were prevalent, and the wind velocity at 10 m above ground was 2.6 m/s for the west wind and 2.62 m/s for the west-southwest wind [21]. And the average relative humidity was 67.2%. ...
Identifying infection transmission routes in hospitals may prevent the spread of respiratory viruses and mass infections. Most previous related research focused on the air movement of passive tracers, which typically represent breathing. In this study, particle evaporation and dispersions with various particle sizes were applied to evaluate particle movement because of breathing and coughing using computational fluid dynamics (CFD) simulations. Pyeongtaek St. Mary Hospital, where a Middle East respiratory syndrome (MERS) index patient infected several patients on the same floor, was used for a case study. We compared the dispersion characteristics of various particle sizes and validated results by comparing infection rates in different ward. Results indicated that droplets spread across the corridor and dispersed to wards that were more than 17 m apart from the index patient by natural ventilation. Droplets from exhaled breath under steady-state simulation showed a wider range of dispersion than cough droplets under transient simulation, but cough droplet dispersion was more consistent with the actual infection rate in each ward. Cough droplets sized under 75 µm evaporated to 26% of the initial size and started to disperse into the corridor within one minute; in nine minutes, droplets dispersed throughout every ward. This study may increase awareness on the dispersion characteristics of infectious particles.
... These demonstrate that air currents are responsible for the dispersal of both aerosols and large droplets within buildings, between different rooms and even between different floors [22,52]. Studies show that this dispersal can be amplified by a variety of factors, including ventilation and air conditioning systems [35], differences of temperature between rooms [53] and air currents entering through open windows [54]. However, ventilation systems are also likely to dilute the concentration of viral particles in the air and thereby to play a potential role in decreasing transmission [22,55]. ...
... This evidence is not specific to SARS-CoV-2. [54] Tracer gas experiments to investigate airflow patterns Moderate -the estimated effect is likely to be close to the true effect but there is a possibility that it is substantially different Study showed that tracer gas was efficiently distributed from room to room along a building corridor, aided by strong air currents entering through open windows [52] Experimental fluid mechanics study using tracer gas to study the transmission of airborne particles around an apartment building ...
Background:
This rapid evidence review identifies and integrates evidence from epidemiology, microbiology and fluid dynamics on the transmission of SARS-CoV-2 in indoor environments.
Methods:
Searches were conducted in May 2020 in PubMed, medRxiv, arXiv, Scopus, WHO COVID-19 database, Compendex & Inspec. We included studies reporting data on any indoor setting except schools, any indoor activities and any potential means of transmission. Articles were screened by a single reviewer, with rejections assessed by a second reviewer. We used Joanna Briggs Institute and Critical Appraisal Skills Programme tools for evaluating epidemiological studies and developed bespoke tools for the evaluation of study types not covered by these instruments. Data extraction and quality assessment were conducted by a single reviewer. We conducted a meta-analysis of secondary attack rates in household transmission. Otherwise, data were synthesised narratively.
Results:
We identified 1573 unique articles. After screening and quality assessment, fifty-eight articles were retained for analysis. Experimental evidence from fluid mechanics and microbiological studies demonstrates that aerosolised transmission is theoretically possible; however, we found no conclusive epidemiological evidence of this occurring. The evidence suggests that ventilation systems have the potential to decrease virus transmission near the source through dilution but to increase transmission further away from the source through dispersal. We found no evidence for faecal-oral transmission. Laboratory studies suggest that the virus survives for longer on smooth surfaces and at lower temperatures. Environmental sampling studies have recovered small amounts of viral RNA from a wide range of frequently touched objects and surfaces; however, epidemiological studies are inconclusive on the extent of fomite transmission. We found many examples of transmission in settings characterised by close and prolonged indoor contact. We estimate a pooled secondary attack rate within households of 11% (95% confidence interval (CI) = 9, 13). There were insufficient data to evaluate the transmission risks associated with specific activities. Workplace challenges related to poverty warrant further investigation as potential risk factors for workplace transmission. Fluid mechanics evidence on the physical properties of droplets generated by coughing, speaking and breathing reinforce the importance of maintaining 2 m social distance to reduce droplet transmission.
Conclusions:
This review provides a snap-shot of evidence on the transmission of SARS-CoV-2 in indoor environments from the early months of the pandemic. The overall quality of the evidence was low. As the quality and quantity of available evidence grows, it will be possible to reach firmer conclusions on the risk factors for and mechanisms of indoor transmission.
... Depending on the specific respiratory virus studied, costs, availability of reagents and desired pathogenesis, different animal models are available for transmission studies 204,206,207 , including mice, guinea pigs, ferrets, syrian hamsters and non-human primates. transgenic or transduced mouse models may also be used to better mimic human pathogenesis when access to non-human primates is limited; for example, transgenic mice expressing the human aCe2 receptor as a model for coronavirus infection 208 . in animal transmission studies, it has been suggested that a minimum of four pairs of donor-contact animals per group is required for sufficient power to detect differences in transmissibility between experimental groups 209 , and this is usually considered as an accepted number to report in studies of influenza virus 210 . ...
Human respiratory virus infections lead to a spectrum of respiratory symptoms and disease severity, contributing to substantial morbidity, mortality and economic losses worldwide, as seen in the COVID-19 pandemic. Belonging to diverse families, respiratory viruses differ in how easy they spread (transmissibility) and the mechanism (modes) of transmission. Transmissibility as estimated by the basic reproduction number (R0) or secondary attack rate is heterogeneous for the same virus. Respiratory viruses can be transmitted via four major modes of transmission: direct (physical) contact, indirect contact (fomite), (large) droplets and (fine) aerosols. We know little about the relative contribution of each mode to the transmission of a particular virus in different settings, and how its variation affects transmissibility and transmission dynamics. Discussion on the particle size threshold between droplets and aerosols and the importance of aerosol transmission for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza virus is ongoing. Mechanistic evidence supports the efficacies of non-pharmaceutical interventions with regard to virus reduction; however, more data are needed on their effectiveness in reducing transmission. Understanding the relative contribution of different modes to transmission is crucial to inform the effectiveness of non-pharmaceutical interventions in the population. Intervening against multiple modes of transmission should be more effective than acting on a single mode.
... Earlier studies succeeded in the detection of the MERS-CoV nucleic acids in the air circulated by an infected camel herd as well as in the people of close contact of this particular herd [5,6]. Meanwhile, several reports showed the possibility of detection of the MERS-CoV nucleic acids in the circulating air in some health care settings during the Korean outbreak of MERS-CoV in 2015 [16,17]. The main goal of the current study was to check the possibility of MERS-CoV shedding in the infected animal breath. ...
... The MERS-CoV case fatality rate started at 52% in 2012 then dropped down to 32% in 2019 [20]. The presence of MERS-CoV in the air of the proximity of patients and infected dromedary camels was previously documented independently by many research groups [6,16,17]. This result confirms that MERS-CoV may be transmitted through droplet infection. ...
Dromedary camels remain the currently identified reservoir for the Middle East respiratory syndrome coronavirus (MERS-CoV). The virus is released in the secretions of the infected camels, especially the nasal tract. The virus shedding curve through the nasal secretions was studied. Although human transmission of the virus through the respiratory tract of close contact people with dromedary reported previously, the exact mechanism of transmission is still largely unknown. The main goal of this study was to check the possibility of MERS-CoV shedding in the exhaled air of the infected camels. To achieve this goal, we conducted a follow-up study in one of the dromedary camel herds, December 2018–April 2019. We tested nasal swabs, breath samples from animals within this herd by the real-time PCR. Our results showed that some of the tested nasal swabs and breath were positive from 24 March 2019 until 7 April 2019. The phylogenetic analysis of the obtained S and N gene sequences revealed the detected viruses are clustering together with some human and camel samples from the eastern region, especially from Al-Hufuf city, as well as some samples from Qatar and Jordon. These results are clearly showing the possibility of shedding of the virus in the breath of the infected camels. This could explain, at least in part, the mechanism of transmission of MERS-CoV from animals to humans. This study is confirming the shedding of MERS-CoV in the exhaled air of the infected camels. Further studies are needed for a better understanding of the MERS-CoV
... X-ray devices, bedrails, and in waiting rooms [5]. It was reported that MERS may spread through poorly ventilated environments as determined using sulfur hexafluoride (SF) tracer gas [6] and computational fluid dynamics analysis [7]. More recently, it has been reported that small virus-laden droplets of SARS-CoV may be displaced by airflow and deposited on equipment such as ventilation equipment, and hospital floors [8]. ...
This study aimed to determine the presence of SARS-CoV-2 on surfaces frequently touched by COVID-19 patients, and assess the scope of contamination and transmissibility in facilities where the outbreaks occurred. In the course of this epidemiological investigation, a total of 80 environmental specimens were collected from 6 hospitals (68 specimens) and 2 "mass facilities" (6 specimens from a rehabilitation center and 6 specimens from an apartment building complex). Specific reverse transcriptase-polymerase chain reaction targeting of RNA-dependent RNA polymerase, and envelope genes, were used to identify the presence of this novel coronavirus. The 68 specimens from 6 hospitals (A, B, C, D, E, and G), where prior disinfection/cleaning had been performed before environmental sampling, tested negative for SARS-CoV-2. However, 2 out of 12 specimens (16.7%) from 2 "mass facilities" (F and H), where prior disinfection/cleaning had not taken place, were positive for SARS-CoV-2 RNA polymerase, and envelope genes. These results suggest that prompt disinfection and cleaning of potentially contaminated surfaces is an effective infection control measure. By inactivating SARS-CoV-2 with disinfection/cleaning the infectivity and transmission of the virus is blocked. This investigation of environmental sampling may help in the understanding of risk assessment of the COVID-19 outbreak in "mass facilities" and provide guidance in using effective disinfectants on contaminated surfaces.
... Since the outbreak of SARS in 2003, there have been an abundance of experimental and/or numerical studies on indoor ventilation and airborne transmission in inter-units of buildings Liu et al., 2011a, b), hospital isolation rooms Saravia et al., 2007;Kao and Yang, 2006;Lai and Cheng, 2007;Shih et al., 2007;Qian et al., 2006;Tung et al., 2009;Qian and Li, 2010;Hang et al., 2014;Sung et al., 2018) or operating rooms (Wang et al., 2018), general indoor environments (Cao et al., 2015;Wei et al., 2018). Besides for vehicle indoor environments, a number of studies emphasized indoor transmission in airplane cabins (Mazumdar et al., 2011;Han et al., 2014;Gupta et al., 2012;Yan et al., 2009) and high-speed train (Zhang and Li, 2012). ...
Droplet dispersion carrying viruses/bacteria in enclosed/crowded buses may induce transmissions of respiratory infectious diseases, but the influencing mechanisms have been rarely investigated. By conducting high-resolution CFD simulations, this paper investigates the evaporation and transport of solid-liquid mixed droplets (initial diameter 10 μm and 50 μm, solid to liquid ratio is 1:9) exhaled in a coach bus with 14 thermal manikins. Five air-conditioning supply directions and ambient relative humidity (RH = 35% and 95%) are considered.
Results show that ventilation effectiveness, RH and initial droplet size significantly influence droplet transmissions in coach bus. 50 μm droplets tend to evaporate completely within 1.8 s and 7 s as RH = 35% and 95% respectively, while 0.2 s or less for 10 μm droplets. Thus 10 μm droplets diffuse farther with wider range than 50 μm droplets which tend to deposit more on surfaces. Droplet dispersion pattern differs due to various interactions of gravity, ventilation flows and the upward thermal body plume. The fractions of droplets suspended in air, deposited on wall surfaces are quantified. This study implies high RH, backward supply direction and passengers sitting at nonadjacent seats can effectively reduce infection risk of droplet transmission in buses. Besides taking masks, regular cleaning is also recommended since 85%-100% of droplets deposit on object surfaces.
... Airflow and ventilation were also implicated as a cause of more efficient spread within hospitals [93]. Although MERS-CoV is known to spread mainly by droplets via close contact, MERS-CoV air droplets can travel long distance significantly larger than 1-2 m if condition allows like a presence of an external airflow [93,94]. ...
... Airflow and ventilation were also implicated as a cause of more efficient spread within hospitals [93]. Although MERS-CoV is known to spread mainly by droplets via close contact, MERS-CoV air droplets can travel long distance significantly larger than 1-2 m if condition allows like a presence of an external airflow [93,94]. Among health care workers, nurses are the most commonly affected followed by physicians and respiratory therapist. ...
Introduction:
Middle East Respiratory Coronavirus Virus (MERS-CoV) first emerged from Saudi Arabia in 2012 and has since been recognized as a significant human respiratory pathogen on a global level.
Methods:
In this narrative review, we focus on the prevention of MERS-CoV. We searched PubMed, Embase, Cochrane, Scopus, and Google Scholar, using the following terms: 'MERS', 'MERS-CoV', 'Middle East respiratory syndrome' in combination with 'prevention' or 'infection control'. We also reviewed the references of each article to further include other studies or reports not identified by the search.
Results:
As of Nov 2019, a total of 2468 laboratory-confirmed cases of MERS-CoV were diagnosed mostly from Middle Eastern regions with a mortality rate of at least 35%. A major outbreak that occurred outside the Middle East (in South Korea) and infections reported from 27 countries. MERS-CoV has gained recognition as a pathogen of global significance. Prevention of MERS-CoV infection is a global public health priority. Healthcare facility transmission and by extension community transmission, the main amplifier of persistent outbreaks, can be prevented through early identification and isolation of infected humans. While MERS-CoV vaccine studies were initially hindered by multiple challenges, recent vaccine development for MERS-CoV is showing promise.
Conclusions:
The main factors leading to sustainability of MERS-CoV infection in high risk courtiers is healthcare facility transmission. MERS-CoV transmission in healthcare facility mainly results from laps in infection control measures and late isolation of suspected cases. Preventive measures for MERS-CoV include disease control in camels, prevention of camel to human transmission.
