Stability of SARS-CoV-2 variants of concern (Delta and Omicron) on surfaces at room temperature

Abstract

Surfaces contaminated with infectious SARS-CoV-2 particles have the potential to cause human infection and any increase in surface survivability of a SARS-CoV-2 variant may increase its prevalence over other variants. This study investigated whether there were differences in surface persistence between Delta and Omicron variants leading to Omicron's dominance globally. Stainless steel coupons were inoculated with suspensions of either Delta or Omicron variant and exposed to typical environmental conditions within a containment level 3 laboratory. Coupons were recovered at different timepoints and enumerated using plaque assay. Both variants were recoverable for >48 h on the coupons. Omicron showed a greater reduction of viability after 48 h compared to Delta with a 20-fold decrease versus 15-fold respectively, but this difference was not statistically significant (p = 0.424). These results indicate that Omicron's surface persistence is unlikely to contribute to it becoming the dominant variant over Delta.

Keywords: Delta; Environmental; Omicron; SARS-CoV-2; Surface persistence; Surface survival.

Fig. 1

Mean titres of viable virus recovered from stainless-steel coupons inoculated with SARS-CoV-2 Delta variant (circles and solid line) and Omicron variant (squares and dotted line). Lines represent linear regression for the variants. Error bars represent standard deviation from three replicates. Dashed line represents limit of detection (5 pfu/coupon).