Differences in environmental stability among SARS-CoV-2 variants of concern: Omicron has higher stability

  1. Ryohei Hirose
  2. Yoshito Itoh
  3. Hiroshi Ikegaya
  4. Hajime Miyazaki
  5. Naoto Watanabe
  6. Takuma Yoshida
  7. Risa Bandou
  8. Tomo Daidoji
  9. Takaaki Nakaya

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Abstract

SARS-CoV-2 variants of concern (VOCs) could cause significant human and economic damage owing to increased infectivity and transmissibility, and understanding their characteristics is crucial for infection control. Here, we analyzed differences in viral stability and disinfection efficacy between the Wuhan strain and all VOCs. On plastic and skin surfaces, Alpha, Beta, Delta, and Omicron variants exhibited more than two-fold longer survival than the Wuhan strain, and the Omicron variant had the longest survival time. Specifically, survival times of the Wuhan strain, Alpha variant, Beta variant, Gamma variant, Delta variant, and Omicron variant on skin surfaces were 8.6 h (95% CI, 6.5–10.9 h), 19.6 h (95% CI, 14.8–25.3 h), 19.1 h (95% CI, 13.9– 25.3 h), 11.0 h (95% CI, 8.1–14.7 h), 16.8 h (95% CI, 13.1–21.1 h), and 21.1 h (95% CI, 15.8– 27.6 h), respectively. In vitro , disinfectant effectiveness evaluations showed that Alpha, Beta, Delta, and Omicron were slightly more resistant to ethanol than the Wuhan strain. However, ex vivo evaluation showed that on human skin, all viruses were completely inactivated by exposure to 35 w/w % ethanol for 15 s. The high environmental stability of these VOCs could increase transmission risk and contribute to spread. Additionally, the Omicron variant might have been replaced by the Delta variant due to its increased environmental stability and rapid spread. To prevent VOC spread, it is highly recommended that current infection control practices use disinfectants with appropriate ethanol concentrations.

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  1. Version published to 10.1101/2022.01.18.476607v2 on bioRxiv
  2. ScreenIT

    SciScore for 10.1101/2022.01.18.476607: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsIRB: Ethical considerations: The study protocol, including sample collection procedures, was reviewed and approved by the Institutional Review Board of the Kyoto Prefectural University of Medicine (ERB-C-1593).
    Consent: Written informed consent was obtained from all the study participants.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Experimental Models: Cell Lines
    SentencesResources
    The titers of the virus were measured in terms of 50% tissue culture infectious dose (TCID50) in VeroE6/TMPRSS2 cells.
    VeroE6/TMPRSS2
    suggested: JCRB Cat# JCRB1819, RRID:CVCL_YQ49)
    Software and Algorithms
    SentencesResources
    For virus culture and quantification, VeroE6/TMPRSS2 cells, expressing the transmembrane serine protease TMPRSS2, were purchased from the Japanese Collection of Research Bioresources Cell Bank (Osaka, Japan) and cultured in Dulbecco’s modified Eagle’s medium (DMEM; Sigma Aldrich) supplemented with 5% fetal bovine serum and G418 (Nacalai Tesque, Kyoto, Japan) (10, 11).
    DMEM; Sigma Aldrich
    suggested: None
    Statistical analysis: Data were analyzed using GraphPad Prism 7 (GraphPad, Inc., La Jolla, CA, USA).
    GraphPad Prism
    suggested: (GraphPad Prism, RRID:SCR_002798)
    GraphPad
    suggested: (GraphPad Prism, RRID:SCR_002798)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    This study had three limitations. First, the reason for the higher environmental stability of Alpha, Beta, Delta, and Omicron variants is unknown at this stage, and evaluation using recombinant viruses might identify factors that determine this. Second, the survival time and half-life obtained in this environmental stability evaluation might vary depending on the external environment and the composition of the body fluid containing the virus. In this study, to accurately analyze the differences in stability between VOCs, the target virus was purified by ultracentrifugation, and PBS was used as a solvent. Third, the relationship between the amount of virus remaining on the surface and the risk of transmission is still unclear at this stage. Therefore, it might be reasonable to interpret the value of survival time in this study as a reference value. In conclusion, we elucidated the environmental stability of VOCs, which is important information for infection control. Furthermore, these findings will contribute greatly to elucidating the mechanism of VOC spread with the addition of genetic analysis.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We found bar graphs of continuous data. We recommend replacing bar graphs with more informative graphics, as many different datasets can lead to the same bar graph. The actual data may suggest different conclusions from the summary statistics. For more information, please see Weissgerber et al (2015).

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  3. Version published to 10.1101/2022.01.18.476607v1 on bioRxiv