Variations in human saliva viscoelasticity affect aerosolization propensity.

Area of Science:

• Fluid dynamics
• Rheology
• Aerosol science

Background:

• Contagious diseases like COVID-19 spread via aerosols and droplets.
• Aerosol formation occurs during respiratory events like sneezing.
• Saliva's properties, like elasticity, influence aerosol generation dynamics.

Purpose of the Study:

• To systematically replicate and study aerosol formation outside the respiratory tract.
• To investigate the role of saliva viscoelasticity in aerosolization.
• To correlate aerosolization propensity with saliva properties and emission conditions.

Main Methods:

• Utilized an impinging jet setup to mimic aerosol formation during sneezing.
• Conducted experiments with human saliva from various donors.
• Performed shear and extensional rheology to quantify viscoelasticity.

Main Results:

• Saliva stability and breakup dynamics varied significantly between individuals.
• Extensional relaxation time was identified as the key measure of saliva elasticity.
• Aerosolization propensity correlated with lower saliva elasticity, higher velocities, and larger volumes.

Conclusions:

• Individual variations in saliva elasticity can affect aerosolization.
• Understanding these variations may explain differences in disease transmission.
• Developed universal state diagrams for aerosolization propensity based on non-dimensional numbers.