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Recovery of Airborne SARS-CoV-2 Virus Surrogate Captured by Filtration: Effect of Sampling and Storage Stress
NIRMALA THOMAS MYERS, Taewon Han, Mei-Ling Li, Gary Brewer, Martin Harper, Gediminas Mainelis, Rutgers, The State University of New Jersey
Abstract Number: 80
Working Group: Infectious Aerosols in the Age of COVID-19
Abstract
Occupational and community exposures to the SARS-CoV-2 virus via the aerosol transmission route is a major concern worldwide. Currently there are no standardized protocols to sample airborne viruses, including SARS-CoV-2, and identify potential exposures. Furthermore, there is limited knowledge on how sampling and storage stress impact the recovery of captured airborne viruses.
Our study analyzed the impact of sampling and storage stress on Human Coronavirus OC43 or HCoV-OC43, a surrogate of SARS-CoV-2 virus, captured by filtration. The HCoV-OC43 virus was aerosolized and then captured by a PTFE filter with PTFE lamination (Zepore) on polypropylene support pad in a conductive plastic cassette (VIRA-PORE, Environmental Express). The effect of sampling stress was evaluated by varying sampling flow rate (3 and 10 L/min) and sampling time (10 and 60 mins). Additional stress was added in a few tests by passing clean air through a filter with the virus on it for 1, 5, and 15 hours. Experiments to determine the effect of storage stress were designed to simulate 2-day transportation of the filter samples to a laboratory (stored at 25°C) and storage up to one week before analysis (stored at room temperature at 25°C and refrigerated conditions at 4°C).
The mode diameter of the aerosolized OC43 virus was 50-60 nm as determined by SMPS and CPC system (TSI Inc.) and MiniWRAS (Grimm Inc.) measurements – to the best of our knowledge, the first reported airborne particle size distribution of HCoV-OC43. Our results showed no significant difference between the virus recovery for the two sampling flow rates, the additional stress of being exposed for 15 hours, and different sampling times (p > 0.05). However, the RNA yield after seven days of storage at room temperature (25°C) was ~2x less compared to storage at refrigerated conditions (4°C). Based on these results, to avoid RNA degradation during transport and storage, we recommend shipping filter samples in a cold container within a week from sampling and store short-term in a laboratory refrigerator (4°C) before analyses. The general recommendations from our study can apply to other filter types as well when used for virus sampling, and we plan to investigate other filter types in our prospective studies.