Researchers identify characteristics that could make someone a super virus spreader

New research from the University of Central Florida has identified physiological characteristics that could make people super-propagators of viruses such as COVID-19.

In a study published this month in the journal Fluid physics, Researchers at UCF’s Department of Mechanical and Aerospace Engineering used computer-generated models to digitally simulate sneezing in different types of people and determine associations between people’s physiological characteristics and the distance their sneeze droplets travel. in the air.

They found that characteristics of people, such as a stuffy nose or a full set of teeth, could increase their potential for spreading viruses by affecting how far droplets travel when sneezing.

According to the United States Centers for Disease Control and Prevention, the main way people get infected with the virus that causes COVID-19 is exposure to respiratory droplets, such as sneezing and coughing that carry infectious viruses. .

Learning more about the factors affecting the distance traveled by these droplets may inform efforts to control their spread, says Michael Kinzel, assistant professor in the Department of Mechanical Engineering at UCF and co-author of the study.

“This is the first study to understand the underlying ‘why’ of distance sneezed,” says Kinzel. “We show that the human body has influencers, such as a complex duct system associated with nasal flow that actually disrupts the spray from your mouth and prevents it from dispersing droplets over long distances.”

For example, when people have a clear nose, such as by blowing it into a tissue, the speed and distance the sneeze droplets travel decrease, according to the study.

This is because a clear nose provides an additional path to the mouth for the sneeze to come out. But when people’s noses are congested, the area in which the sneeze can come out is restricted, resulting in an increase in the speed of the sneezing droplets being expelled from the mouth.

Likewise, the teeth also restrict the sneeze exit area and increase the speed of the droplets.

“The teeth create a narrowing effect in the jet that makes it stronger and more turbulent,” explains Kinzel. “They actually seem to be causing transmission. So if you see someone without teeth, you can expect a weaker sneeze pattern from them.”

To perform the study, the researchers used 3D modeling and numerical simulations to recreate four types of mouths and noses: 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 expelled droplets when a person has a congested nose and a full set of teeth is about 60% greater than when they don’t. does not.

The results indicate that when someone keeps their nose clear, such as by blowing it into a tissue, they could reduce the distance their germs travel.

The researchers also simulated three types of saliva: thin, medium and thick.

They found that thinner saliva caused sneezing made up of smaller droplets, which created a spray and stayed in the air longer than medium, thick saliva.

For example, three seconds after a sneeze, when the thick saliva reached the floor and thus lessened its threat, the thinner saliva was still floating in the air as a potential disease transmitter.

The work is linked to the researchers’ project to create a COVID-19 cough lozenge that would give people thicker saliva to reduce the distance that droplets travel from a sneeze or cough, and thus reduce the probability of disease transmission.

The results provide new insight into the variability in exposure distance and indicate how physiological factors affect rates of transmissibility, says Kareem Ahmed, associate professor in the Department of Mechanical and Aerospace Engineering at UCF and co-author of the ‘study.

“The results show that the exposure levels strongly depend on fluid dynamics which can vary depending on several human characteristics,” explains Ahmed. “Such characteristics may be underlying factors in the spread of events in the COVID-19 pandemic.”

The researchers say they hope to move the work forward into clinical studies then to compare their simulation results with those of real people from various backgrounds.

Co-authors of the study were Douglas Fontes, postdoctoral researcher at Florida Space Institute and lead author of the study, and Jonathan Reyes, postdoctoral researcher in the Department of Mechanical and Aerospace Engineering at UCF.

Fontes says that to advance the study’s conclusions, the research team wants to study the interactions between gas flow, mucous film, and tissue structures in the upper respiratory tract during respiratory events.

“Numerical models and experimental techniques should work side by side to provide accurate predictions of primary rupture within the upper respiratory tract during these events,” he says.

“This research will potentially provide information for more precise safety measures and solutions to reduce the transmission of pathogens, providing better conditions for dealing with common diseases or pandemics in the future,” he says.