Environmental Stability of SARS-CoV-2 on Different Types of Surfaces under Indoor and Seasonal Climate Conditions

Abstract

Transmission of severe acute respiratory coronavirus 2 (SARS-CoV-2) mainly occurs through direct contact with an infected person via droplets. A potential role of contaminated surfaces in SARS-CoV-2 transmission has been suggested since the virus has been extensively detected on environmental surfaces. These findings have driven the investigation of virus stability on surfaces under several conditions. However, it remains unclear how long the infectious virus survives on surfaces under different climate conditions, which could play a role in predicting the seasonality of SARS-CoV-2. Therefore, the aim of this study was to estimate the virus stability and its biological half-life on various types of surfaces under indoor and seasonal climate conditions. This study revealed that SARS-CoV-2 survived the longest on surfaces under winter conditions, with a survival post-contamination on most surfaces up to 21 days, followed by spring/fall conditions, with a survival up to 7 days. Infectious virus was isolated up to 4 days post-contamination under indoor conditions, whereas no infectious virus was found at 3 days post-contamination under summer conditions. Our study demonstrates the remarkable persistence of SARS-CoV-2 on many different common surfaces, especially under winter conditions, and raises awareness to the potential risk of contaminated surfaces to spread the virus.

Keywords: SARS-CoV-2; environmental stability; fomite; virus decay.

Figure 1

Stability of severe acute respiratory coronavirus 2 (SARS-CoV-2) on different types of surfaces. Each graph represents the virus decay on a defined surface. For this study, 50 μL of virus inoculum (5 × 10⁴ 50% tissue culture infectious dose (TCID₅₀)) was added onto each material and dried for 4.5 h inside a biosafety cabinet. The virus survival was evaluated under the four following conditions: at 21 °C/60% relative humidity (RH) (grey), 25 °C/70% RH (red), 13 °C/66% RH (green), and 5 °C/75% RH (blue). The infectious virus was recovered at 0.19 (after drying period, and equal to 4.5 h), 1, 2, 3, and 4 days post-contamination (dpc) at 21 °C/60% RH and 25 °C/70% RH, 0.19, 1, 3, 5, and 7 dpc at 13 °C/66% RH and 0.19, 1, 3, 6, 10, 15, and 21 dpc at 5 °C/75% RH. Virus titer at each time point was expressed as mean log10 transformed titer with standard deviation. Virus titers at time points when at least one replicate was positive were incorporated to estimate linear regression models; the solid line and its shaded area represent an estimated best fit model and 95% confidence intervals, respectively. Limit of detection (LOD) in each titration assay was 10^0.968 TCID₅₀, and a negative result is represented as a half value of LOD, 10^0.667 TCID₅₀. The dash line shows LOD in triplicate, 10^0.767 TCID₅₀, when there was LOD in one replicate, but negative in two other replicates. Adjusted p-value between two slopes of linear regression models is represented as * (p < 0.05), ** (p < 0.01), *** (p < 0.001), and **** (p < 0.0001).