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Published on: November 5, 2021
Infectivity of SARS-CoV-2 on Inanimate Surfaces: Don't Trust Ct Value.
Johannes K Knobloch1, Susanne Pfefferle2, Marc Lütgehetmann2
1Institute for Medical Microbiology, Virology and Hygiene, Department for Infection Prevention and Control, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany.
Quantitative PCR (qPCR) Ct values may not reliably indicate SARS-CoV-2 infectivity on surfaces. Effective disinfection reduced viable virus, yet Ct values remained unchanged, suggesting qPCR is unsuitable for predicting surface contamination risk.
Area of Science:
- Environmental Microbiology
- Infectious Diseases
- Molecular Diagnostics
Background:
- SARS-CoV-2 RNA detection on surfaces is common, raising questions about viral load and infectivity.
- Quantitative PCR (qPCR) is used to detect viral RNA, but its correlation with surface infectivity is unclear.
Purpose of the Study:
- To evaluate if Ct values from qPCR can predict the infectivity of SARS-CoV-2 on contaminated surfaces.
- To assess the impact of disinfection on viral RNA persistence and infectivity.
Main Methods:
- Investigated SARS-CoV-2 RNA on ICU surfaces and attempted virus isolation.
- Used surrogate bacteriophage Φ6 to test disinfection efficacy and Ct value changes.
- Applied UV-C, alcoholic disinfectant, and ozone for disinfection.
Main Results:
- SARS-CoV-2 RNA was found on 37/143 surfaces, but virus isolation failed, even from high-load surfaces.
- Disinfection reduced Φ6 viability significantly.
- UV-C and alcohol disinfection showed minimal change in Φ6 Ct values despite viability loss.
- Ozone disinfection degraded Φ6 RNA, causing detectable Ct value shifts.
Conclusions:
- Quantitative PCR Ct values are not suitable for predicting SARS-CoV-2 infectivity on inanimate surfaces.
- Ct values should not be used as markers for surface contamination infectivity in clinical settings.
