Evaluation of Residual Infectivity after SARS-CoV-2 Aerosol Transmission in a Controlled Laboratory Setting

Abstract

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is mainly transmitted through respiratory droplets, aerosols, or direct contact with fomites from an infected subject. It has been reported that SARS-CoV-2 is stable and viable in aerosol up to 16 h in controlled laboratory conditions. However, the aerosolization conditions varied a lot between the studies. In this work, an experimental laboratory model of SARS-CoV-2 aerosolization was established, employing an impinger nebulizer, a cylindrical chamber for aerosol travel, and a SKC biosampler for the collection of particles. The efficiency of the system was assessed based on the molecular determination of the viral load in the nebulizer after the aerosolization and in the aerosol collected at the end of the travel. Moreover, the residual infectivity was tested in vitro on the Vero E6 cell line, through the observation of the cytopathic effect (CPE), and the quantification of the viral load in the supernatants at 7 days post inoculation (dpi). A high RNA viral load was found in the SKC biosampler after aerosolization, indicating that it was possible to transport a high virus titer through the 30-cm chamber with all the dilutions (initial 105, 104, 103 plaque forming unit—PFU/mL). At the 7 dpi, an increment of the RNA viral load was determined for the dilutions 105 and 104 PFU/mL tested, while only the initial 105 PFU/mL resulted in visible CPE. Our findings allowed us to achieve the resilience of SARS-CoV-2 in aerosol form, at a concentration comparable to those reported for clinical samples. This mode of transmission should be considered for the mitigation and preventive measures to counteract SARS-CoV-2 spreading.

Evaluation of Three Automated Extraction Systems for the Detection of SARS-CoV-2 from Clinical Respiratory Specimens

“…As of 21 December 2021, more than 274 million confirmed cases and 5.3 million deaths due to COVID-19 had been reported [3]. SARS-CoV-2 is predominantly transmitted by exposure to respiratory droplets and aerosol particles [4]. As SARS-CoV-2 is easily transmitted through the air and has a relatively long incubation time, several types and grades of measures, including travel restrictions, social distancing, and limitations on movement, have been adopted by the governments to prevent the spread of this virus [5][6][7].…”

A new laser device for ultra-rapid and sustainable aerosol sterilization

“…This relies on a constant airflow at the inlet of the aerosol dispenser with attenuated pressure, so that microbial particles are not inactivated by mechanical stress. This renders it rather unique in comparison to existing nebulizers for which the effect of aerosolization on viral and bacterial load has been tested using biochemical quantification of structural components of viral particles (either proteins or genomes), which not necessarily correlates with viability and infectivity ( Zupin et al, 2021 ). When functional infectivity tests were performed, this showed that microbes were inactivated by aerosolization or in other cases, no quantitative results were numerated ( Allegra et al, 2016 , [27] ).…”

Operative Protocol for Testing the Efficacy of Nasal Filters in Preventing Airborne Transmission of SARS-CoV-2

“…The present protocol evolves from our experimental model of SARS-CoV-2 aerosol generation and transmission employing a BLAM bioaerosol generator, a cylindrical chamber for aerosol travel and a swirling bioaerosol collector SKC Biosampler for the collection of the particles [ 23 ], and from the experimental model for assessing the SARS-CoV-2 filtering efficacy of face masks published during 2020 by Ueki and coworkers [ 24 ]. An 8-Jet BLAM nebulizer operated as Multi Pass Atomizer mimics the spread of virus particles from a COVID-19 positive emitter patient (8 L per minute) while the SKC Biosampler sucks air at flow comparable to that of human breath inspiration (12.5 L per minute).…”

“…The efficiency of the bio-aerosol nebulization and transmission system is assessed after the aerosolization determining the viral load in the SKC sampler compared to that remaining in the nebulizer. Effectiveness of Biogel silver nanoparticle (AgNP) endonasal filters inserted into the Y shaped tube sampling port, connected to the SKC sampler simulating nose inhalation, is evaluated, measuring infective viruses that pass through the endonasal filters and are collected in the SKC bio-sampler reservoir, by use of a plaque forming unit (PFU) assay and quantitative reverse transcription real-time PCR (qRT-PCR) [ 23 ].…”