Modeling the initial phase of SARS-CoV-2 deposition in the respiratory tract mimicked by the (11)C radionuclide

Evangelista, Heitor; Amaral, César; Porto, Luís Cristóvão; Gonçalves Junior, Sérgio J.; Delfino Sodré, Eduardo; Nogueira, Juliana; dos Santos, Angela M. G.; Cataldo, Marcio; Junger, Daniel

The knowledge on the deposition and retention of the viral particle of SARS-CoV-2 in the respiratory tract during the very initial intake from the ambient air is of prime importance to understand the infectious process and COVID-19 initial symptoms. We propose to use a modified version of a widely tested lung deposition model developed by the ICRP, in the context of the ICRP Publication 66, that provides deposition patterns of microparticles in different lung compartments. In the model, we mimicked the "environmental decay" of the virus, determined by controlled experiments related to normal speeches, by the radionuclide (11)C that presents comparable decay rates. Our results confirm clinical observations on the high virus retentions observed in the extrathoracic region and the lesser fraction on the alveolar section (in the order of 5), which may shed light on physiopathology of clinical events as well on the minimal inoculum required to establish infection.