The term superspreader has gotten much attention during the COVID-19 pandemic. It is used to describe infected individuals who can spread the virus to several people (within the time that they are contagious) and drive disease outbreaks. The basic reproduction number of COVID-19 is estimated to be about three, this means a contagious person can potentially infect three healthy people. However, superspreaders have been seen to infect many more people – more than even 100 people in some cases.
Now, a group of researchers at the University of Central Florida claim that by studying the dynamics of sneezing, they have found the reason why some people are superspreaders – something that not many studies have covered so far.
The findings of the study are published in the journal Physics of Fluids.
The researchers used computer models to study the dispersion of droplets from a sneeze from various people by changing multiple factors including their anatomy, health, stress and gender.
In particular, the following variations were studied: effects of the properties of the saliva, effects of the structure of the buccal cavity and nasal passage and how they change by the person.
Two features, in particular, were found to be associated with increased risk of superspreading – nasal congestion and a full set of teeth.
It was found that nasal congestion led to a 300 percent increase in droplets content at a distance of six feet. In a news release by the University of Central Florida, the authors of the study explained that a clear nose provides easy passage to sneeze droplets; however, in case of congestion, there is no way for the droplets to come out easily. So, the sneeze droplets come out with a higher velocity through the mouth.
A similar effect is seen in people with a full set of teeth, where the teeth restrict the passage of sneeze droplets.
The study suggested that those with a full set of teeth and a congested nose had a 60 percent higher spread of sneeze droplets than those who did not.
Additionally, those with thinner saliva produced smaller sneeze droplets that stayed in the air for longer periods of time.
We already know that people who release more droplets while sneezing or coughing are more likely to be superspreaders.
A previous study done at the Massachusetts Institute of Technology indicated that several factors, especially the viral load (the amount of virus in a person’s body) determine if a patient will be a superspreader.
However, there is no estimate for the number of viral particles released during severe infection. Also, it has been indicated that SARS-CoV-2, even if it is present in the aerosols, may not be as effective in spreading the disease since the number of viral particles present in the droplets may not be enough. The speed at which the droplets settle down on surfaces would determine the risk of airborne transmission.
A recent study done at MIT had indicated that superspreading events play a much larger role in spreading COVID-19 than had been anticipated.
For more information, read our article on Who are superspreaders and how to stop them.
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