SARS-CoV-2 Dynamics in the Mucus Layer of the Human Upper Respiratory Tract Based on Host–Cell Dynamics

Abstract

A thorough understanding of the inhalation dynamics of infectious aerosols indoors and infection dynamics within the host by inhaled viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) plays an important role in the assessment and control of infection risks indoors. Here, by combining computational fluid–particle dynamics (CFPD) and host–cell dynamics (HCD), SARS-CoV-2 infection dynamics in the mucus layer of the human upper airway were studied. To reproduce the diffusive and convective transport of the virus in the nasal cavity–nasopharynx by mucociliary motion, a three-dimensional (3D)-shell model with a mucus layer was developed. The initial virus concentrations for HCD calculation were estimated based on the deposition distribution of droplets with representative sizes analyzed by CFPD. To develop a new HCD model, the target-cell-limited model was integrated with the convection–diffusion equation. Additionally, the sensitivity of the infection rate β to the infection dynamics was systematically investigated. The results showed that the time series of SARS-CoV-2 concentration in the mucus layer strongly depended on diffusion, convection, and β. Although the SARS-CoV-2 dynamics obtained here have not been verified by corresponding clinical data, they can preliminarily reveal its transmission mode in the upper airway, which will contribute to the prevention and treatment of coronavirus disease 2019.

Large eddy simulation of droplet transport and deposition in the human respiratory tract to evaluate inhalation risk

“…Finally, although more exhaustive models of infection risk have been proposed [ 60 ], we have calculated the inhalation risk based on the infection probability dose-response model proposed by Wells [ 61 ] and improved by Riley [ 62 ] due to its simplicity, defined as: …”

Numerical investigations of exhaling respiratory aerosol from inside of the human respiratory tract

“…These suspended aerosol can linger for some time in the environment before being inhaled by uninfected individuals. Once inhaled, these virus-loaded aerosol droplets can settle on the inner walls of the respiratory airway, paving the way for viral invasion of the immune system and subsequent infections (CDC 2023;Liu et al 2017;Li et al 2022;Wang et al 2021;Cowling et al 2023;Jarvis 2020;Kutter et al 2018). Therefore, the quantity of exhaled aerosol droplets released into the external environment is directly connected to the risk of virus transmission (Guo et al 2022;Xu 2019;Hofer et al 2021).…”

COVID infection in 4 steps: Thermodynamic considerations reveal how viral mucosal diffusion, target receptor affinity and furin cleavage act in concert to drive the nature and degree of infection in human COVID-19 disease

“…Previously we highlighted the significance of the shedding of SARS-CoV2 from the epithelium of nasopharyngeal tissues from an infected individual to its subsequent attachment to the ACE2 viral target on the nasal epithelial cells of a new host [ 14 ]. As indicated by Li et al [ 38 ], virus enters the upper respiratory tract after virus containing droplets are deposited on the mucus layer on the airway surface. This initial interaction with the mucosal surface and the activities immediately following this contact are pivotal in COVID-19 disease.…”