When fluid mechanics meets virology: a modeling framework for respiratory infection onset and projection of viral infectious dose*

Synergizing airflow-induced inhaled particulate dynamics inside the nose, with clinical prognosis as well as virologic and epidemiologic data, can address questions like: (a) what are the hazardous particulate sizes predominantly responsible for a respiratory infection onset, or (b) what might be the minimum number of virions (i.e. the infectious dose) that can trigger an infection. This talk presents an extendable modeling framework to answer (a) and (b), in the context of SARS-CoV-2 transmission. The study combines computational fluid dynamics tracking of inhaled transport, with sputum assessments from hospitalized patients and prior measurements of speech ejecta sizes. To capture a variety of breathing conditions, four inhalation rates are simulated: 15, 30, 55, 85 L/min. The lower rate (i.e.15 L/min) replicates comfortable resting breathing with viscous-laminar steady-state physics; at higher rates, we apply Large Eddy Simulation. Regional deposition of virus-laden particulates at nasopharynx, which is the main initial infection site for SARS-CoV-2, peaks for the aerosol/droplet size range of 2.5–19 μm. Also, the infectious dose is projected at a remarkably low order of hundreds, underlining high viral transmissibility. See Basu, Scientific Reports, 11(1), 2021, for details.