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27th January 2022
The Omicron Covid variant is environmentally stable and can survive for at least 21 hours on human skin and 193 hours on plastic surfaces. This was the finding by a team from the Department of Infectious Diseases, Kyoto Prefectural University of Medicine, Kyoto, Japan.
The Omicron variant has numerous mutations which have likely led to enhanced transmissibility. One potential factor associated with greater transmissibility is the spread from contact with human skin. The stability of the original COVID-19 variant on human skin has been found to be 9 hours which is considerably longer than the human influenza A virus. While some evidence has revealed how both the B.1.1.7 and B.1.351 covid variants had similar levels of surface stability, there is a lack of comparative data for all of the currently identified variants.
For the present study, the Japanese team examined the environmental stability of several circulating variants of concern, including the Omicron variant and compared this to the original Wuhan strain. They also sought to determine the disinfectant efficacy against the different strains. The stability was tested on human skin samples collected from forensic autopsy specimens approximately one day after death. The stability of the variants was also evaluated on plastic (polystyrene plates).
In all experiments, samples were applied to the surface of either skin or plastic and incubated and the amount of remaining viable virus determined. They defined the survival time as the time until virus could no longer be detected and each experiment was conducted three times.
Omicron covid variant survival
When tested on plastic surfaces, the Wuhan strain survived for 56 hours (95% CI 39 – 76.7 hours) whereas the omicron variant survived for 193.5 hours (95% CI 153.1 – 236.2 hours). For comparative purposes, the delta variant survived a similar length of time (114 hours).
When tested on human skin, the Wuhan strain survived for 8.6 hours (95% CI 6.5 – 10.9 hours) whereas the omicron variant lasted 21.1 hours (95% CI 15.8 – 27.6 hours). The Delta variant also survived longer than the Wuhan strain, lasting 16.8 hours (95% CI 13.1 – 21.1 hours).
In the presence of a 40% ethanol solution, the omicron covid variant was completely inactivated within 15 seconds. Furthermore, on human skin, all strains were completely inactivated after 15 seconds with exposure to 35% ethanol.
Discussing their findings, the authors noted how the Omicron variant appeared to survive on plastic surfaces for much longer than the Wuhan strain and that this enhanced environmental stability could be an important factor with the increased level of transmissibility of the variant. They added that since the variant is completely inactivated after 15 seconds, this highlighted the importance of continued infection control measures such as hand hygiene.
Hirose R et al. Differences in environmental stability among SARS-CoV-2 variants of concern: Omicron has higher stability BioRxiv 2022