Such information is essential for taking appropriate action to reduce or eliminate the probability of infection in both community and health care environments. The travel distance of the cough airflow, taken with the dispersion characteristics of expired droplets, are of particular interest. There is one peak of the droplet number concentration in the sub-micron range and another peak at over 10 μm. Wells first defined large droplets as those over 100 μm in aerodynamic diameter. The number of droplets during a single cough can be as high as 3,000, with varying totals among different experiments. In general, much less is known about the mechanism and control of short-range airborne exposure than about long-range airborne routes.Ĭoughing has been more extensively investigated than breathing and sneezing in disease transmission. Beyond 1–2 m, the exhaled air stream dissolves into the room airflow, and the pathogen-containing droplets or droplet nuclei are dispersed according to the global airflow in the room. Short-range airborne exposure via smaller droplets or droplet nuclei is also important in close proximity infection.
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The former is known as direct spray infection, in which relatively large (≥ 5 μm in diameter) droplets or droplet nuclei can be directly deposited on the nasal or oral mucosa of the new host. Exposure to these pathogen-containing droplets can occur via both short- (within 1–2 m of the source patient) and long- (beyond about 2 m in the indoor environment) range routes. These droplets and droplet nuclei can contain elements such as sodium, potassium and chloride in solutes DNA, lipids, glycoproteins and proteins in suspended insoluble solids and, of course, infectious pathogens if released by an infectious patient. Once exhaled, droplets evaporate and become droplet nuclei. Thousands of droplets per respiration can be released during breathing, coughing and sneezing. The human cough is known to be a significant vector for transmitting respiratory diseases in indoor environments. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: All relevant data are within the paper.įunding: This study received financial support from National Natural Science Foundation of China (, 51278440, YL) and The Research Grants Council (, 17205014, YL). Received: SeptemAccepted: DecemPublished: January 3, 2017Ĭopyright: © 2017 Wei, Li. PLoS ONE 12(1):Įditor: Roi Gurka, Coastal Carolina University, UNITED STATES Moreover, the leading vortex plays an important role in enhancing particle transport.Ĭitation: Wei J, Li Y (2017) Human Cough as a Two-Stage Jet and Its Role in Particle Transport. The water tank experiments revealed that although medium and large particles deposit readily, their maximum spread distance is similar to that of small particles. A protocol was developed to scale the particle experiments between the prototype in air, and the model in water. However, the effects of Re c and Q/ AD on the maximum penetration distances proved to be more significant larger values of Re c and Q/ AD reflected cough flows with greater penetration distances. The real-cough and sinusoidal cases exhibited greater penetration ability than the pulsation cases under the same characteristic Reynolds number (Re c) and normalized cough expired volume ( Q/AD, with Q as the cough expired volume and A as the opening area). During the starting-jet stage, the flow rate is a function of time three temporal profiles of the exit velocity (pulsation, sinusoidal and real-cough) were investigated in this study, and our results showed that the cough flow’s maximum penetration distance was in the range of a 50.6–85.5 opening diameter ( D) under our experimental conditions. The cough flow is characterized as a two-stage jet specifically, the starting jet (when the cough starts and flow is released) and interrupted jet (after the source supply is terminated).
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The human cough is a significant vector in the transmission of respiratory diseases in indoor environments.