Walking fast in corridors increases Covid infection risk

Picture a speeding boat leaving a wake in water as it moves. Similar to this, when a person walking in a corridor coughs, their breath expels droplets that form a trail in the air around them.

A study has revealed the existence of a “re-circulation bubble” directly behind the person’s torso and a long wake streaming out behind them at approximately waist height, with flow patterns strongly related to the shape of the human body.

This trail of droplets, if produced by someone infected with Covid-19, puts those walking behind the person at an increased risk of contracting the virus.

This is after a team of scientists at the Chinese Academy of Sciences used computational simulations to accurately predict airflow and how droplets are dispersed in different environments to understand how the virus is spread.

After determining the airflow patterns, the researchers modeled the dispersal of droplets expelled from the simulated person’s mouth. They found the shape of the environment around the person had a huge effect on how droplets were dispersed.

Their findings settled on two dispersal modes; one where the droplets moved from the mouth to form a bubble that floats far behind the moving person. In the other mode, the droplets were closely attached to the person’s back, trailing behind them like a tail as they moved.

The team concluded that children were at more risk of this type of transmission because in both modes, the droplets moved about half the height of the infected person, which is around the mouth level for children.