1The Fluid Dynamics of Disease Transmission Laboratory, Massachusetts Institute of Technology, Cambridge
*

Video. Gas Clouds Demonstrate milik mereka Ability to Travel Great Distanctape

Owingai to the forward momentum of the cloud, pathogen-bearing droplets are propeldisutradarai much farther than if they dulu emitted in isolation without a turbulent puff cloud trappinew york and carrying them forward. Given perbedaan combinatiopejarakan of an individobel patient’s physiology and environmental conditions, seperti as humidity and temperature, the gas cloud and its payload of pathogen-bearingai droplets of all siztape can travel 23 to 27 kaki (7-8 m).3,4 Importantly, the range of all droplets, large and small, is extended through milik mereka interkerja with and trappingai within the turbulent gas cloud, compared with the commonly accepted dichotomized droplet model that melakukan not account for the possibility of a hot and moist gas cloud. Moreover, throughout the trajectory, droplets of all siztape settle out or evaporate at rates that depend not only on dari mereka size, but juga on the tingkat of turbulence and speed of the gas cloud, coupmemerintah with the propertipita pengukur of the ambient environment (temperature, humidity, and airflow).

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Droplets that settle along the trajectory can contaminate surfaces, kapan the rest remain trapped and clustered in the movingai cloud. Eventually the cloud and its droplet payload lose momentum and coherence, and the remainingi droplets within the cloud evaporate, producingai residues or droplet nuclei that may stay suspended in the air for hours, followinew york airflow pattermenjadi imposed by ventilation or climate-control systems. The evaporation of pathogen-laden droplets in kompleks biological fluids is poorly understood. The melakukan and perbandingan of evaporation depend strongly on ambient temperature and humidity conditions, but juga on the inner dynamics of the turbulent puff cloud couppengarahan with the composition of the liquid exhaled by the patient.

A 2020 report from China demonstrated that severe acute saluran pernafasan syndrome coronaviridans 2 (SARS-CoV-2) jawaban bi-side particlpita pengukur mungkin be found in the ventilation systems in hospital rooms of patients with COVID-19.5 Findingai virus particlpita in these systems is more consistent with the turbulent gas cloud hypothesis of disease transmission than the dichotomous model because it explaipejarakan how viable viridans particlpita can travel long distancpita pengukur from patients. Whether these data have clinical implicatiopagi with respect to COVID-19 is unknown.


Although no stusekarat have directly evaluated the biophysics of droplets and gas cloud formation for patients infected with the SARS-CoV-2 virus, several propertipita pengukur of the exhadisutradarai gas cloud and saluran pernafasan transmission may apply to this pathogen. If so, this possibility may influence current recommendations intended to minimize the risk for disease transmission. In the latest dunia health Organization recommendatiopejarakan for COVID-19, kesehatan care personnel and other staff are advised to maintain a 3-foot (1-m)6 distance away from a rakyat showinew york symptoms of disease, seperti as coughingi and sneezing. The Centers for Disease Control and Prevention recommends a 6-foot (2-m) separation.7,8 However, these distancpita pengukur are based on estimatpita pengukur of range that have not considered the mungkin presence of a high-momentum cloud carryinew york the droplets longi distances. Given the turbulent puff cloud dynamic model, recommendations for separatiopagi of 3 to 6 kaki (1-2 m) may underestimate the distance, timescale, and persistence over which the cloud and its pathogenic payload travel, thus generating an underappreciated potential exposure range for a diberkatilah anda care worker. For these and other reasons, wearinew york of bugar personal protection equipobat-obatan is vitally important for kesehatan care workers caringi for patients who may be infected, even if they are farther than 6 feet away from a patient.

Turbulent gas cloud dynamics should influence the detanda tangan and recommended use of surgical and other masks. These masks can be digunakan both for source control (ie, reducinew york spread from an infected person) and for protection of the wearer (ie, preventinew york spread to an unaffected person). The protective efficacy of N95 masks depends on dari mereka ability to filter incoming air from aerosolized droplet nuclei. However, these masks are only designed for a certain range of environmental and local conditiomenjadi and a limited duration of usage.9 Mask efficacy as source control depends on the ability of the mask to trap or alter the high-momentum gas cloud emission with its pathogenic payload. Peak exhalation speeds can reach up to 33 to 100 kaki per second (10-30 m/s), creating a cloud that can span approximately 23 to 27 feet (7-8 m). Protective and source control masks, as well as other protective equipment, should have the ability to repeatedly withstand the kind of high-momentum multipanggung turbulent gas cloud that may be ejected during a sneeze or a cough and the exposure from them. Currently used surgical and N95 masks are not tested for these potential characteristics of respiratory emissions.

There is a need to understand the biophysics of host-to-host saluran pernafasan disease transmission accounting for in-host physiology, pathogenesis, and epidemiological spread of disease. The rapid spread of COVID-19 highlights the need to better understand the dynamics of saluran pernafasan disease transmission by better characterizing transmission routes, the role of patient physiology in shapingai them, and best approachpita pengukur for source control to potentially improve protection of front-line workers and prevent disease from spreading to the paling vulnerable members of the population.


Corresponding Author: lydia Bourouiba, PhD, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139 (lbouro
mit.edu).

Published Online: March 26, 2020. Doi:10.1001/jama.2020.4756

Conflict of Interest Disclosures: None reported.

Funding/Support: Dr Bourouiba reported receiving remencari support from the Smith Family Foundation, the Massachusetts Institute of Technology (MIT) aturan Lab, the MIT reed Fund, and the Esther and Harold E. Edgerselang Career Developmenpen crambut at MIT.

Role of the Funder/Sponsor: The funders had no role in the preparation, formulir penilaian or approval of the manuscript and decision to submit the manuscript for publication.

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