{"id":3513,"date":"2021-02-06T13:25:59","date_gmt":"2021-02-06T13:25:59","guid":{"rendered":"http:\/\/thales.mit.edu\/bush\/?page_id=3513"},"modified":"2021-11-30T05:18:17","modified_gmt":"2021-11-30T05:18:17","slug":"covid-19","status":"publish","type":"page","link":"https:\/\/thales.mit.edu\/bush\/index.php\/covid-19\/","title":{"rendered":"Fluid dynamics of the pandemic"},"content":{"rendered":"\n<div class=\"wp-block-cover alignwide has-subtle-background-color has-background-dim is-style-twentytwentyone-border\"><div class=\"wp-block-cover__inner-container is-layout-flow wp-block-cover-is-layout-flow\">\n<h3 class=\"has-text-align-center wp-block-heading\">Fluid dynamics of the pandemic<\/h3>\n\n\n\n<div id=\"block-213a723d-bd14-49d7-8813-00596a2416eb\" class=\"wp-block-image is-style-twentytwentyone-border\"><figure class=\"alignright is-resized\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/thales.mit.edu\/bush\/wp-content\/uploads\/2021\/03\/Color-cough.jpeg\" alt=\"This image has an empty alt attribute; its file name is Color-cough.jpeg\" width=\"417\" height=\"307\"\/><\/figure><\/div>\n\n\n\n<p class=\"tw-text-wide wp-block-paragraph\" id=\"block-73cdd24a-375d-48be-b8aa-1a51db05ac46\" style=\"font-size:17px\">Respiratory diseases such as COVID-19 are transported on the respiratory droplets exhaled by an infected person.  In 2014, with <a href=\"https:\/\/cee.mit.edu\/people_individual\/lydia-bourouiba\/\">Lydia Bourouiba<\/a> (now on the faculty in Civil and Environmental Engineering at MIT) we undertook an integrated experimental and theoretical study of the dynamics of coughing and sneezing. Our study made clear that, contrary to the prevailing wisdom at the time, small respiratory drops are transported farther than larger drops, because they are suspended by the gas flows associated with exhalation, which take the form of either turbulent jets (for normal breathing) or turbulent vortex rings (for coughing and sneezing). In more recent work with my colleague <a href=\"https:\/\/www.mit.edu\/~bazant\/\">Martin Bazant<\/a>, I have considered the fate of the smallest such pathogen-bearing droplets, that may be mixed uniformly throughout an indoor space by ambient air flows.<br><\/p>\n\n\n<ul class=\"wp-block-latest-posts__list is-grid columns-4 alignwide tw-img-ratio-1-1 tw-heading-size-small tw-stretched-link is-style-twentytwentyone-latest-posts-dividers wp-block-latest-posts\"><li><div class=\"wp-block-latest-posts__featured-image\"><img loading=\"lazy\" decoding=\"async\" width=\"150\" height=\"117\" src=\"https:\/\/thales.mit.edu\/bush\/wp-content\/uploads\/2021\/02\/cough-1.jpg\" class=\"attachment-thumbnail size-thumbnail wp-post-image\" alt=\"\" style=\"width:100%;height:77.78%;max-width:1152px;\" \/><\/div><a class=\"wp-block-latest-posts__post-title\" href=\"https:\/\/thales.mit.edu\/bush\/index.php\/2021\/04\/05\/the-dynamics-of-coughing-and-sneezing\/\">Violent expiratory events: on coughing and sneezing<\/a><\/li>\n<li><div class=\"wp-block-latest-posts__featured-image\"><img loading=\"lazy\" decoding=\"async\" width=\"150\" height=\"120\" src=\"https:\/\/thales.mit.edu\/bush\/wp-content\/uploads\/2021\/03\/SneezeEjecta-1.png\" class=\"attachment-thumbnail size-thumbnail wp-post-image\" alt=\"\" style=\"width:100%;height:80.07%;max-width:552px;\" \/><\/div><a class=\"wp-block-latest-posts__post-title\" href=\"https:\/\/thales.mit.edu\/bush\/index.php\/2021\/04\/05\/visualizing-sneeze-ejecta\/\">Visualizing sneeze ejecta and respiratory droplets<\/a><\/li>\n<li><div class=\"wp-block-latest-posts__featured-image\"><img loading=\"lazy\" decoding=\"async\" width=\"150\" height=\"144\" src=\"https:\/\/thales.mit.edu\/bush\/wp-content\/uploads\/2021\/04\/Beyond6ft-thumb.png\" class=\"attachment-thumbnail size-thumbnail wp-post-image\" alt=\"\" style=\"width:100%;height:96.04%;max-width:556px;\" \/><\/div><a class=\"wp-block-latest-posts__post-title\" href=\"https:\/\/thales.mit.edu\/bush\/index.php\/2021\/04\/01\/beyond-six-feet-a-guideline-to-limit-indoor-airborne-transmission-of-covid-19\/\">New COVID-19 indoor safety guideline<\/a><\/li>\n<li><div class=\"wp-block-latest-posts__featured-image\"><img loading=\"lazy\" decoding=\"async\" width=\"150\" height=\"138\" src=\"https:\/\/thales.mit.edu\/bush\/wp-content\/uploads\/2021\/04\/CO2JMB.jpg\" class=\"attachment-thumbnail size-thumbnail wp-post-image\" alt=\"\" style=\"width:100%;height:92.33%;max-width:339px;\" \/><\/div><a class=\"wp-block-latest-posts__post-title\" href=\"https:\/\/thales.mit.edu\/bush\/index.php\/2021\/03\/22\/monitoring-co2-to-quantify-the-risk-of-indoor-airborne-transmission-of-covid-19\/\">Monitoring CO2 for indoor COVID-19 safety<\/a><\/li>\n<\/ul>\n\n\n<p class=\"tw-text-wide wp-block-paragraph\" id=\"block-e9ece7b3-fef7-475a-a1cf-126b464715f2\" style=\"font-size:17px\">The `Six-Foot Rule&#8217;, the safety guideline intended to mitigate the transmission of COVID-19, only protects one from the large, millimeter-scale droplets that can travel no farther than 6 feet, and offers no protection from the micron-scale droplets that may be suspended indefinitely and mixed uniformly through an indoor space. It is now widely believed that COVID-19 is spread primarily via airborne transmission, specifically, by inhalation of these micron-scale respiratory droplets. With <a href=\"https:\/\/www.mit.edu\/~bazant\/\">Martin Bazant<\/a>, we developed a new <a href=\"https:\/\/www.pnas.org\/content\/118\/17\/e2018995118.short\" target=\"_blank\" rel=\"noreferrer noopener\">Safety Guideline<\/a> for mitigating such Indoor Airborne Transmission of COVID-19 and other respiratory illnesses. This guideline suggests a limit on the Cumulative Exposure Time, the product of the number of the people in a particular indoor space and the time spent in that space. The manner in which the Cumulative Exposure Time depends on various factors, including ventilation rate, room volume and human activity, is succinctly stated in our Equation (5).<\/p>\n\n\n\n<p class=\"has-text-align-left tw-text-wide wp-block-paragraph\" style=\"font-size:17px\">Most recently, we have deduced how to <a href=\"https:\/\/www.medrxiv.org\/content\/10.1101\/2021.04.04.21254903v1\" target=\"_blank\" rel=\"noreferrer noopener\">use carbon-dioxide monitors in conjunction with our new Safety Guideline<\/a> to provide a real-time assessment of the risk of COVID-19 and other airborne respiratory diseases  in indoor spaces.<\/p>\n<\/div><\/div>\n\n\n\n<div class=\"wp-block-columns alignwide is-layout-flex wp-container-core-columns-is-layout-8f761849 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<div class=\"wp-block-cover has-purple-background-color has-background-dim is-style-twentytwentyone-border\" style=\"min-height:323px;aspect-ratio:unset;\"><div class=\"wp-block-cover__inner-container is-layout-flow wp-block-cover-is-layout-flow\">\n<h4 class=\"alignwide has-text-align-center wp-block-heading\">Explore COVID-19 risk<\/h4>\n\n\n\n<p class=\"tw-text-wide wp-block-paragraph\" style=\"font-size:17px\">Our work prompted Kasim Khan to develop an online App, which can be used to assess COVID-19 risks in various scenarios. It uses our\u00a0theoretical model\u00a0to calculate safe exposure times and occupancy levels for indoor spaces. By adjusting room specifications, ventilation and filtration rates, face-mask usage, respiratory activities, risk tolerance and more, one can see how to mitigate indoor COVID-19 transmission in different indoor spaces.<\/p>\n\n\n\n<div class=\"wp-block-buttons alignwide is-content-justification-center is-layout-flex wp-block-buttons-is-layout-flex\">\n<div class=\"wp-block-button is-style-outline is-style-outline--1\"><a class=\"wp-block-button__link has-background\" href=\"https:\/\/indoor-covid-safety.herokuapp.com\/?units=metric\" style=\"background-color:#9b1e47\" target=\"_blank\" rel=\"noreferrer noopener\">try the app<\/a><\/div>\n<\/div>\n<\/div><\/div>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<div class=\"wp-block-cover has-subtle-background-color has-background-dim is-style-twentytwentyone-border\" style=\"min-height:323px;aspect-ratio:unset;\"><div class=\"wp-block-cover__inner-container is-layout-flow wp-block-cover-is-layout-flow\">\n<h4 class=\"alignwide has-text-align-center wp-block-heading\">Learn more<\/h4>\n\n\n\n<p class=\"tw-text-wide wp-block-paragraph\" style=\"font-size:17px\">  <br>Additional related information about indoor airborne transmission of COVID-19 and other respiratory diseases may be found on Martin Bazant&#8217;s <a href=\"http:\/\/web.mit.edu\/bazant\/www\/COVID-19\/\">COVID-19 webpage<\/a>.<\/p>\n<\/div><\/div>\n<\/div>\n<\/div>\n\n\n\n<div class=\"wp-block-group is-style-default\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\"><\/div><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":2,"featured_media":4501,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"tw-no-title.php","meta":{"footnotes":""},"class_list":["post-3513","page","type-page","status-publish","has-post-thumbnail","hentry","entry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v16.3 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Fluid dynamics of the pandemic - John W. 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