THURSDAY, December 17, 2020 (HealthDay News) – You may want to think twice before entering a hallway with strangers during the pandemic: Researchers report that following a person walking quickly with COVID-19 in a narrow hallway can increase your risk of infection, even if you keep your distance.
That’s because that person can leave behind long streams of virus-laden droplets, according to a study published Dec. 15 in the journal. Fluid physics.
The risk is particularly high for children.
The results come from computer simulations that evaluated airflow and droplet dispersion patterns behind walkers at different locations.
Previous simulations focused on large open interior spaces, but did not take into account the effect of nearby walls, such as those in a narrow hallway.
If a person walking in a hallway cough, they expel droplets that spin around and behind their bodies, forming a wake much the way a moving boat leaves a wake in the water, the researchers said.
And people who cough have a “recirculation bubble” directly behind their torso and a long trail of droplets flowing behind them at about waist height.
“The flow patterns we found are closely related to the shape of the human body,” said study co-author Xiaolei Yang, from the Chinese Academy of Sciences in Beijing. “2 meters downstream, the wake is almost negligible at mouth and leg height but is still visible at waist height.”
Researchers have identified two modes of droplet propagation.
In one, the cloud of droplets leaves the person moving and lingers far behind them, creating a drifting cloud loaded with viruses.
In the other mode, the cloud of droplets remains attached to the person, trailing behind them like a tail.
Here is a photo of the two types of spread:
“For the detached mode, the droplet concentration is much higher than for the attached mode, five seconds after a cough,” Yang said in a press release. “It poses a great challenge in determining safe social distancing in places like a very narrow hallway, where a person can inhale viral droplets even if the patient is far ahead.”
Children are at particular risk in both scenarios, as the droplet clouds persist above the ground at about half the height of an infected adult – or at the level of a child’s mouth / nose. .
U.S. Centers for Disease Control and Prevention Explain how to protect yourself and others from COVID-19.
SOURCE: Fluid physics, press release, December 15, 2020