Environmental Studies; SARS-CoV-2; computational fluid and particle dynamics; host–cell dynamics; mucus layer; mucociliary motion; upper respiratory tract; Infections; Inhalation; Mucus; Mathematical models; Severe acute respiratory syndrome coronavirus 2; Influenza; Drugs; Viruses; Computer applications; Dynamic tests; COVID-19; Convection; Viral diseases; Respiratory tract; Convection-diffusion equation; Case studies; Coronaviruses; Respiratory system; Respiration; Diffusion; Severe acute respiratory syndrome; Dynamics; Three dimensional models; Nasopharynx; Diffusion layers; Nose; Diffusion rate; Viral infections; Three dimensional motion; Respiratory diseases; Health risks; Disease transmission