A question we've all no doubt asked over the past year is: how far can a cough travel? Well, as a new study shows, the shape of an indoor space might change the trajectory and dispersal of potentially virus-laden particles coughed out by a person. 

In a new study, simulations suggested that long streams of cough-generated droplets can trail behind an infected person if they quickly walk down a narrow corridor. This, the researchers argue, suggests narrow corridors and tight spaces could potentially increase the risk of transmitting Covid-19.

As reported in the journal Physics of Fluids, researchers from the Chinese Academy of Sciences used computer simulations and 3D modeling to understand how the movement of cough-generated droplets from a walking person changed depending on the surrounding indoor space. The team’s work has previously looked at how windows, air conditioners, and other objects might affect the airflow and droplet dispersal in certain rooms. For this new work, they looked closely at the effect of nearby walls and tight corridors.

They found that if an infected person coughs while walking down a corridor, a concentrated cloud of droplets will trail behind them for over 2 meters (over 6 feet). On the other hand, a cough in an open space will form a less concentrated — potentially less infectious as there is a lower viral load — cloud of droplets around them. However, the cloud of droplets coughed out in a narrow corridor start to drop towards the floor fairly quickly, reaching waist-height about 2 seconds after the cough. According to the study, this indicates that children walking behind an infectious patient could be exposed to higher transmission risk than adults, being shorter.

"The flow patterns we found are strongly related to the shape of the human body," Xiaolei Yang, study author from the Institute of Mechanics at the Chinese Academy of Sciences, said in a statement. "At 2 meters downstream, the wake is almost negligible at mouth height and leg height but is still visible at waist height."

A number of other computer simulations have been carried out to understand how coughs, sneezes, and virus-laden droplets behave in the air under different circumstances. 

One recent bit of research looked to identify different features that might make people a so-called “superspreader” of viral infections, thought to be a major driver of the Covid-19 outbreak. They found used 3D modeling and computer simulations to show that sneezes from people who have a blocked nose and a full set of teeth travel about 60 percent farther than those who don’t. 

Another study used a manikin head to examine the effectiveness of different mask types at stopping the dispersal of virus-laden droplets from the mouth and nose. The conclusion: face masks work, but some are more effective at stopping the spread of coughs and sneezes than others. 

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