key: cord-0809855-vm4x7xgu
authors: Meister, Toni Luise; Fortmann, Jill; Todt, Daniel; Heinen, Natalie; Ludwig, Alfred; Brüggemann, Yannick; Elsner, Carina; Dittmer, Ulf; Steinmann, Joerg; Pfaender, Stephanie; Steinmann, Eike
title: Comparable environmental stability and disinfection profiles of the currently circulating SARS-CoV-2 variants of concern B.1.1.7 and B.1.351
date: 2021-05-16
journal: J Infect Dis
DOI: 10.1093/infdis/jiab260
sha: 2a7675a9ec5506f8b5a0a01bcd2a10cf46493849
doc_id: 809855
cord_uid: vm4x7xgu

The emergence of novel SARS-CoV-2 B.1.1.7 and B.1.351 variants of concern with increased transmission dynamics has raised questions regarding stability and disinfection of these viruses. In this study, we analyzed surface stability and disinfection of the currently circulating SARS-CoV-2 variants B.1.1.7 and B.1.351 compared to the wild type. Treatment with heat, soap and ethanol revealed similar inactivation profiles indicative of a comparable susceptibility towards disinfection. Furthermore, we observed comparable surface stability on steel, silver, copper and face masks. Overall, our data support the application of currently recommended hygiene concepts to minimize the risk of B.1.1.7 and B.1.351 transmission.

M a n u s c r i p t 2

Since the outbreak of Severe Acute respiratory Syndrome Coronavirus-2 (SARS-CoV-2) at the end of 2019, > 120 million cases and > 2.8 million death (March 31 st 2021) have been reported [1] . Viral evolution includes the natural emergence of viral variants, which can encode for a variety of mutations in their genome compared to the parental wild type virus. Mutations which confer either enhanced fitness, higher pathogenicity, better transmissibility or immune escape are of special concern as they could significantly influence transmission dynamics and thereby potentially sustain epidemic growth. In-dependent lineages of SARS-CoV-2 have recently been reported: UK, B.1.1.7; South Africa, B.1.351; and Brazil, P.1 [2] . Importantly, these variants of concern (VOC) display higher reproduction numbers than preexisting variants and consequently increase incidences in various countries. Moreover, VOCs have been associated with more severe course of infection and/or potential immune escape due to multiple changes in the immunodominant spike protein [3] . The B.1.1.7 variant has accumulated 23 mutations, including 14 non-synonymous substitutions and was not phylogenetically related to the variants circulating in the UK when it was detected [4] . The B.1.351 variant has 12 non-synonymous mutations and one deletion. Approximately 77% of these mutations are located in the spike protein while the remaining ones are located in ORF1a, envelope (E), and N viral proteins [3] . Since the global access to COVID-19 vaccines is still limited, diligent attention on transmission-based precautions is essential to limit VOC spread.

However, given the rapid spread and increased transmission dynamics of the emerging variants, concerns regarding the effectiveness of current hygiene measures and inactivation strategies have been raised, which could be lowered by the genetic alterations. Here we compared the stability of three SARS-CoV-2 strains, A c c e p t e d M a n u s c r i p t 3 the preexisting B1. 1 

For SARS-CoV-2 virus suspension preparation, Vero E6 cells (kindly provided by C.

Drosten and M. Müller) were seeded at 2×10 6 

To analyze viral stability on different surfaces we performed time kinetics and studied viral stability over 48 h in three independent experiments. Therefore, stainless steel disk, disks sputtered with copper or silver, the inner layer of surgical masks and according to EN 5.2.2.8) and was adjusted to 5×10 6 TCID 50 /mL. Immediately, 10 min, 1 h, 24 h and 48 h after virus inoculation on the different surfaces they were placed aseptically in a 2 mL DMEM (without FCS) harboring container and vortexed for 60 s. To determine the amount of recovered infectious virus from the test specimen an end-point-dilution assay was performed on Vero E6 cells to calculate the remaining TCID 50 according to Spearman and Kärber .

To test susceptibility to disinfection, viruses were exposed to 20, 30, 40, 60 and 80 we compared viral inactivation upon usage of ethanol, a common ingredient of several disinfectants and recommended by the World Health Organization (WHO) in resource limited countries [5] . Viruses were exposed towards increasing concentrations of ethanol for 30 s and residual viral infectivity was determined by endpoint titration. In accordance to previous results, all three viral variants could be efficiently inactivated upon treatment with at least 30 % (v/v) ethanol for 30 s, confirming equal susceptibility towards disinfection (Fig. 1A, left panel) . These results were supported by a subsequent regression analysis, which revealed comparable inactivation kinetics (Fig. 1A, comparable inactivation kinetics (Fig. 1B, right panel) . Next, we addressed susceptibility of the three strains towards heat (56 °C) and observed a decrease in viral titers towards background levels within 30 min (Fig. 1C, left panel) . Importantly, inactivation kinetics were comparable between all viral variants ( Figure 1C , right panel). Although SARS-CoV-2 is mainly transmitted through respiratory droplets and aerosols exhaled from infected individuals, transmission via fomites cannot be excluded. Viral stability was examined on representative materials surfaces: silver, copper and stainless-steel discs for up to 48 h, using an initial virus concentration of 9.2 × 10 6 TCID 50 /mL. Importantly, all variants remained infectious on the different surfaces for 48 h and compared to the wild type virus no differences in the relative infectivity were observed ( Fig. 2A and suppl. Table 1 ). In order to mimic a potential contamination of on protective masks by infected individuals, we contaminated the inside of either a surgical mask or a FFP2 mask and analyzed viral stability for all variants. Again, comparable residual titers of all VOCs were observed over time ( Fig.   2B and suppl. Table 1 ). In conclusion, the currently circulating VOC did not exhibit Heat inactivation protocols are commonly used for a variety of subsequent applications, therefore, we aimed to address the susceptibility of VOCs towards treatment with 56 °C for different times. As described before, a 30 min treatment with 56 °C is sufficient to efficiently abolish infectivity, with no differences between the VOCs. Of note, these inactivation experiments have been performed with lab-grown viruses in permissive eukaryotic cells and therefore do not consider additional factors (i.e. mucus and/or salvia) and might differ from the specific infectivity of patientderived SARS-CoV-2 particles.Transmission via contaminated surfaces (fomites) is not considered to be a main route of infection with SARS-CoV-2 [10] . However, given the high transmission rates of the VOCs, questions and concerns regarding enhanced environmental stability have been raised. Surface stability for several days has been described under laboratory conditions for several coronaviruses [11] [12] [13] .

Using different surfaces, we did not observe any differences regarding viral decay kinetics. Importantly, we observed prolonged stability of all variants on face masks, highlighting the importance of exchanging masks regularly and the risk of shared masks. Of note, in contrast to other publications [14] , we did not observe an antiviral effect of silver surfaces on SARS-CoV-2. This is in contrast to copper, for which antiviral properties have been described before and could be confirmed in this study [15] . In conclusion, our results suggest that current hygiene measures are also appropriate and effective against the currently circulating VOCs. A c c e p t e d M a n u s c r i p t 10 

Home -Johns Hopkins Coronavirus Resource Center

Available at

Emerging SARS-CoV-2 Variants and Impact in Global Vaccination Programs against SARS-CoV-2/COVID-19

SARS-CoV-2 one year on: evidence for ongoing viral adaptation

WHO Guidelines on Hand Hygiene in Health Care: First Global Patient Safety Challenge. Clean Care is Safer Care

Estimated transmissibility and impact of SARS-CoV-2 lineage B.1.1.7 in England

Human error: models and management

Inactivation of Severe Acute Respiratory Syndrome Coronavirus 2 by WHO-Recommended Hand Rub Formulations and Alcohols

A Method to Test the Efficacy of Handwashing for the Removal of Emerging Infectious Pathogens

Low risk of SARS-CoV-2 transmission by fomites in real-life conditions

Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents

Stability of SARS-CoV-2 in different environmental conditions

Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1

Potent antiviral effect of silver nanoparticles on SARS-CoV-2

Sars-CoV-2 (COVID-19) inactivation capability of copper-coated touch surface fabricated by cold-spray technology

We thank Thorsten Wolff, Jessica Schulz 

All No reported conflicts of interest. 

A c c e p t e d M a n u s c r i p t 11 A c c e p t e d M a n u s c r i p t 12 A c c e p t e d M a n u s c r i p t