Modeling the load of SARS-CoV-2 virus in human expelled particles during coughing and speaking

Abstract

Particle size is an essential factor when considering the fate and transport of virus-containing droplets expelled by human, because it determines the deposition pattern in the human respiratory system and the evolution of droplets by evaporation and gravitational settling. However, the evolution of virus-containing droplets and the size-dependent viral load have not been studied in detail. The lack of this information leads to uncertainties in understanding the airborne transmission of respiratory diseases, such as the COVID-19. In this study, through a set of differential equations describing the evolution of respiratory droplets and by using the SARS-CoV-2 virus as an example, we investigated the distribution of airborne virus in human expelled particles from coughing and speaking. More specifically, by calculating the vertical distances traveled by the respiratory droplets, we examined the number of viruses that can remain airborne and the size of particles carrying these airborne viruses after different elapsed times. From a single cough, a person with a high viral load in respiratory fluid (2.35 × 10 9 copies per ml) may generate as many as 1.23 × 10 5 copies of viruses that can remain airborne after 10 seconds, compared to 386 copies of a normal patient (7.00 × 10 6 copies per ml). Masking, however, can effectively block around 94% of the viruses that may otherwise remain airborne after 10 seconds. Our study found that no clear size boundary exists between particles that can settle and can remain airborne. The results from this study challenge the conventional understanding of disease transmission routes through airborne and droplet mechanisms. We suggest that a complete understanding of the respiratory droplet evolution is essential and needed to identify the transmission mechanisms of respiratory diseases.

Effects of surgical masks on droplet and aerosol dispersion under various oxygen delivery modalities

“…Third, the particle quantification experiment was performed at a mild down flow, which might affect the natural distance of dispersion, and the design of the quantification experiment limited the detection area of particles. Forth, particles with a size of less than 0.5 µm were not detectable in our study; however, these smaller particles are not speculated to contain enough viruses for transmission (17). To date, the virus load of SARS-CoV-2 in aerosols generated from coughing or included in exhaled breath from patients with COVID-19 has not been reported (18), although SARS-CoV-2 has been found to be viable in room air for 3 hours (19).…”

Nebulized CLODOS Technology Shows Clear Virucidal Properties against the Human Coronavirus HCoV-229E at Non-Cytotoxic Doses

“…It must be taken into account that these tests have been carried out starting from a stock of HCoV-229E with a high titer, and that, on average, the viral load found in aerosols or on surfaces may be significantly similar [ 24 ]. Prior experiments showed that 1 min of loud speaking could produce thousands of droplet nuclei per second, each containing approximately 1000 viral particles, starting from an average viral load of 7 × 10 6 per mL [ 25 , 26 ].…”

Establishing an Analogue Based In Silico Pipeline in the Pursuit of Novel Inhibitory Scaffolds against the SARS Coronavirus 2 Papain-Like Protease

“…Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [ 6 ], the causative agent of COVID-19 [ 7 ], is the seventh known coronavirus to infect humans [ 8 ]. SARS-CoV-2 is highly infectious [ 9 , 10 , 11 , 12 ], and spreads through particles expelled from infected individuals [ 13 , 14 ]. As the most severe pandemic caused by a coronavirus [ 15 ], COVID-19 has caused more cases and fatalities than the severe acute respiratory syndrome (SARS) pandemic, and the Middle East respiratory syndrome (MERS)-related outbreaks, combined [ 16 ].…”