Research

Fluid Dynamics and Disease Transmission

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Right now people around the world are experiencing daily disruptions as a result of the recently declared coronavirus pandemic. There is a lot we don’t know yet about coronavirus, though researchers are working around the clock to report new information. Today’s video, though a couple years old, focuses on an area of medical knowledge that’s historically lacking but extremely relevant to our current situation: the mechanics behind disease transmission through sneezing or coughing.

High-speed imagery of a sneeze cloud.

Lydia Bourouiba is a leader in this area of research. Her studies have focused not on the size range of droplets produced but on the dynamics of the turbulent clouds that carry these droplets and what allows them to persist and spread. If you’ve wondered just why healthcare providers are recommending masks for sick people, keeping large distances between individuals, and frequent hand-washing, the image above hopefully helps explain why. Droplets carried in these turbulent clouds can travel several meters, and the buoyancy of the cloud’s gas components can help lift droplets toward ceiling ventilation. Right now, social distancing is one of our best tools against this disease transmission.

My goal in posting this is not to panic anyone. Rather, I hope you leave better informed as to why these precautions are needed. With coronavirus, our detailed knowledge of its characteristics — how long it remains viable in the air or on surfaces, how much is needed for an infection to take hold, etc. — is limited. But from research like Bourouiba’s, we know that coughing and sneezing are remarkably efficient ways to deliver respiratory pathogens, and that’s why caution is warranted. Stay safe, readers. (Video credit: TEDMED; image credit: Bourouiba Research Group, source; research credit: L. Bourouiba et al., see also S. Poulain and L. Bourouiba, pdf)

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