Infectivity of SARS-CoV-2 on Inanimate Surfaces: Don’t Trust Ct Value

Johannes K. Knobloch (), Susanne Pfefferle, Marc Lütgehetmann, Dominik Nörz, Eva M. Klupp, Cristina E. Belmar Campos, Stefan Kluge, Martin Aepfelbacher, Birte Knobling and Gefion Franke
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Johannes K. Knobloch: Institute for Medical Microbiology, Virology and Hygiene, Department for Infection Prevention and Control, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
Susanne Pfefferle: Institute for Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
Marc Lütgehetmann: Institute for Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
Dominik Nörz: Institute for Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
Eva M. Klupp: Institute for Medical Microbiology, Virology and Hygiene, Department for Infection Prevention and Control, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
Cristina E. Belmar Campos: Institute for Medical Microbiology, Virology and Hygiene, Department for Infection Prevention and Control, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
Stefan Kluge: Department of Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
Martin Aepfelbacher: Institute for Medical Microbiology, Virology and Hygiene, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
Birte Knobling: Institute for Medical Microbiology, Virology and Hygiene, Department for Infection Prevention and Control, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
Gefion Franke: Institute for Medical Microbiology, Virology and Hygiene, Department for Infection Prevention and Control, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany

IJERPH, 2022, vol. 19, issue 24, 1-9

Abstract: SARS-CoV-2 RNA is frequently identified in patient rooms and it was speculated that the viral load quantified by PCR might correlate with infectivity of surfaces. To evaluate Ct values for the prediction of infectivity, we investigated contaminated surfaces and Ct-value changes after disinfection. Viral RNA was detected on 37 of 143 investigated surfaces of an ICU. However, virus isolation failed for surfaces with a high viral RNA load. Also, SARS-CoV-2 could not be cultivated from surfaces artificially contaminated with patient specimens. In order to evaluate the significance of Ct values more precisely, we used surrogate enveloped bacteriophage Φ6. A strong reduction in Φ6 was achieved by three different disinfection methods. Despite a strong reduction in viability almost no change in the Ct values was observed for UV-C and alcoholic surface disinfectant. Disinfection using ozone resulted in a lack of Φ6 recovery as well as a detectable shift in Ct values indicating strong degradation of the viral RNA. The observed lack of significant effects on the detectable viral RNA after effective disinfection suggest that quantitative PCR is not suitable for predicting the infectivity of SARS-CoV-2 on inanimate surfaces. Ct values should therefore not be considered as markers for infectivity in this context.

Keywords: SARS-CoV-2; surface contamination; quantitative PCR; Ct value; disinfection (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2022
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