Coughs, sneezes travel farther than you might think

A MIT researcher studying the physics coughs and sneezes found they can can travel up to 27 feet at speeds of up to 60 miles per hour, highlighting the need for covering your cough.

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CDC guidance on covering coughs and sneezes
Tony Rice
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Research published online last week in The Journal of the American Medical Association found coughs and sneezes can carry 7-8 meters (23-26 feet) at speeds of 10-30 m/s (22-67 miles per hour). Bourouiba hopes her research will help the World Health Organization (WHO) and Centers for Disease Control improve distancing guidance to prevent spread as well as design better protective gear, especially for medical workers on the front lines outbreaks like COVID-19.

You can do your part by maintaining distances recommended by the WHO and CDC and follow CDC guidance to cough or sneeze into a tissue when possible or your upper arm otherwise.

Dr. Lydia Bourouiba, a researcher studying the physics of disease transmission in humans, animals and plants, raised new information in efforts to limit the spread of the coronavirus. Her research measured transmission of droplets s using high speed video and lighting techniques to better understand their trajectories.

"The locally moist and warm atmosphere [of a cough or sneeze] allows the contained droplets to evade evaporation for much longer than occurs with isolated droplets. Under these conditions, the lifetime of a droplet could be considerably extended." according to Dr. Bourouiba

Research on how droplets from exhalations settle around an infected individual date back to the late 1800s. William Wells' study of tuberculosis transmission in the 1930s found that large droplets which tend to settle near an infected individual, while smaller droplets tend to evaporate leaving material which travels further.

High speed video of droplets transmitted by a cough (courtesy: JAMA/MIT Fluid Dynamics of Disease Transmission Laboratory) How effectively a virus is transmitted in these small vs large droplets is core to recommendations by the The World Health Organization and Centers for Disease Control and Prevention according to Dr. Bourouiba.

“Epidemics have shaped human history throughout time. Today we want to be sure that the full depth of understanding from all corners of science are leveraged to mitigate epidemics and save lives.” says Bourouiba

How a virus survives in large vs large droplets is still today at the core of the classification systems of routes of respiratory disease transmission adopted by the World Health Organization and other agencies, such as the Centers for Disease Control and Prevention


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