Viable SARS-CoV-2 Delta Variant Detected in Aerosols in a Residential Setting with a Self-Isolating College Student with COVID-19

WILLIAM VASS, John Lednicky, Sripriya Nannu Shankar, Z. Hugh Fan, Arantzazu Eiguren-Fernandez, Chang-Yu Wu, University of Florida

     Abstract Number: 94
     Working Group: Aerosol Science of Infectious Diseases: What We Have Learned and Still Need to Know about Transmission, Prevention, and the One Health Concept

Abstract
By September 2021, the B.1.617.2 (Delta) variant of SARS-CoV-2 comprised over 99% of genome-sequenced COVID-19 cases of the United States. The rise in cases due to the Delta variant, which coincided with a return to in-person school attendance, strained mitigation plans implemented by educational institutions. Some plans required sick students to self-isolate off-campus, which may potentially result in unintended exposure of cohabitants during self-isolation.

We collected air and surface samples from a single-family home used by a self-isolating university student with mild COVID-19 to assess the presence of SARS-CoV-2. We deployed the three-stage NIOSH bioaerosol sampler (Model BC-251), which allowed aerosol particle size fractionation by using dual cyclone stages and a final filter stage (Cao et al., 2010). We also used a Bio-Spot Viable Virus Aerosol Sampler (BioSpot-VIVAS), which collects viruses using water condensation growth technology (CGT) and improves virus preservability (Lednicky, et al., 2020). We placed air samplers >2 m away from the student who was resting on their bed. Dual sampler types were used to improve the chances of maintaining virus viability and to discern the distribution of particle sizes containing SARS-CoV-2. In addition, high-touch surfaces were sampled using sterile nylon swabs.

SARS-CoV-2 RNA was detected by reverse-transcription polymerase chain reaction (RT-PCR) in air samples from both the isolation bedroom and a distal, non-isolation room. Results from the size-fractionated sampling revealed that SARS-CoV-2 was primarily within particles with diameters < 4.4 µm. This is significant because particles in that size range are capable of passing ciliated airways and potentially infecting cells within the lower respiratory tract (Pan et al., 2019). Among eight collected surface samples, only the swab taken from the student’s mobile phone resulted in SARS-CoV-2 detection. Viable SARS-CoV-2 in air samples collected by BioSpot-VIVAS (292 PFU/L and 132 PFU/L) and the phone swab (1000 PFU/cm2) was isolated for further analysis. Genomic sequencing revealed that the virus was a Delta variant.

This work confirmed the presence of viable SARS-CoV-2 within and beyond the isolation bedroom of a person with COVID-19, which shows potential risk of transmitting virus beyond isolation spaces in residences through the airborne route. The results also showed improved ability to culture SARS-CoV-2 with the CGT method relative to cyclones and filters.