Sampling and recovery of infectious SARS-CoV-2 from high-touch surfaces by sponge stick and macrofoam swab

Abstract

Effective sampling for severe acute respiratory syndrome 2 (SARS-CoV-2) is a common approach for monitoring disinfection efficacy and effective environmental surveillance. This study evaluated sampling efficiency and limits of detection (LODs) of macrofoam swab and sponge stick sampling methods for recovering infectious SARS-CoV-2 and viral RNA (vRNA) from surfaces. Macrofoam swab and sponge stick methods were evaluated for collection of SARS-CoV-2 suspended in a soil load from 6-in² coupons composed of four materials: stainless steel (SS), acrylonitrile butadiene styrene (ABS) plastic, bus seat fabric, and Formica. Recovery of infectious SARS-CoV-2 was more efficient than vRNA recovery on all materials except Formica (macrofoam swab sampling) and ABS (sponge stick sampling). Macrofoam swab sampling recovered significantly more vRNA from Formica than ABS and SS, and sponge stick sampling recovered significantly more vRNA from ABS than Formica and SS, suggesting that material and sampling method choice can affect surveillance results. Time since initial contamination significantly affected infectious virus recovery from all materials, with vRNA recovery showing limited to no difference, suggesting that SARS-CoV-2 vRNA can remain detectable after viral infectivity has dissipated. This study showed that a complex relationship exists between sampling method, material, time from contamination to sampling, and recovery of SARS-CoV-2. In conclusion, data show that careful consideration be used when selecting surface types for sampling and interpreting SARS-CoV-2 vRNA recovery with respect to presence of infectious virus.

Keywords:

• Limit of detection
• sampling efficiency
• SARS-CoV-2 recovery
• surface sampling

Acknowledgements

We thank Lindsay A. Catlin for assistance with RT-qPCR and K. T. Vandergrif and Dr. Christopher Dibble at Battelle Memorial Institute for helpful technical discussions. The EPA, through its Office of Research and Development, directed the research described herein conducted through contract EP-C-16-014, task order 68HERC20F0241 with Battelle Memorial Institute. It has been subjected to review by the EPA’s Office of Research and Development and approved for publication. Approval does not signify that the contents reflect the views of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

Data availability statement

All data are publicly available at data.gov.