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Using computer-generated models, scientists simulated sneezing in different types of people and identified biological characteristics that could make a person super spread of viruses such as the new coronavirus that causes Covid-19.
The study, published in the journal Physics of Fluids, determined associations between people’s physiological characteristics and the distance traveled by sneezing droplets and staying in the air.
According to scientists, including those from the University of Central Florida (UCF) in the United States, people’s characteristics, such as a stuffy nose or a full set of teeth, could increase their potential for virus spread by influencing the distance the droplets travel. when they sneeze.
The U.S. Centers for Disease Control and Prevention had previously noted that the primary way people become infected with the new coronavirus is through exposure to respiratory droplets, such as sneezing and coughing, which carry infectious viruses.
Knowing more about the factors that influence the distance these droplets travel can inform efforts to control their spread, said study co-author Michael Kinzel of UCF.
“This is the first study that aims to understand the ‘why’ behind how far sneezing travel,” Kinzel said.
“We show that the human body has influencers, such as a complex system of ducts associated with the nasal flow that actually stops the jet from the mouth and prevents it from dispersing droplets over great distances,” he added.
Citing an example, the researchers said that when people have a clean nose, such as by blowing it into a handkerchief, the speed and distance traveled by the sneezing droplets decrease.
This is because a clear nose provides a path beyond the mouth for the sneeze to exit, they added.
However, when people’s noses are congested, the area from which the sneeze can exit is limited, thus causing an increase in the rate of sneeze droplets expelled from the mouth, the study noted.
According to scientists, the teeth also narrow the sneeze exit area and increase the speed of the droplets.
“The teeth create a shrinking effect in the jet that makes it stronger and more turbulent,” said Kinzel.
“They actually seem to drive the transmission. So if you see someone with no teeth, you can actually expect a fainter sneeze jet from them,” he added.
In the research, the scientists used 3D modeling and numerical simulations to recreate four types of mouth and nose: a person with clear teeth and nose, a person without teeth and a clear nose, a person without teeth and a congested nose, and a person. with congested teeth and nose.
When they simulated sneezing in the different models, they found that the spray distance of the droplets expelled when a person has a congested nose and a full set of teeth is about 60% greater than when they don’t.
The results revealed that when someone keeps their nose clean, such as blowing it into a handkerchief, it could reduce the distance traveled by germs.
The researchers also simulated three types of saliva: thin, medium and thick.
They found that the thinner saliva resulted in sneezing made up of smaller droplets, which created a spray and stayed in the air longer than average, thick saliva.
The results provide new insight into the variability of exposure distance and indicate how physiological factors affect transmissibility rates, said Kareem Ahmed, another co-author of the UCF study.
“The results show that exposure levels are highly dependent on fluid dynamics which can vary with different human characteristics,” Ahmed said.
“Such characteristics may be the factors behind superspreading events in the Covid-19 pandemic,” he added.
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