Results from an experimental study from Japan published on the preprint server bioRxiv show that the Omicron SARS-CoV-2 variant lives for a longer time on plastic and skin compared to the delta variant.

The variants examined included the original Wuhan strain, Alpha variant (B.1.1.7), Beta variant (B.1.351), Gamma variant (P.1), Delta variant (B.1.617.2) and the latest variant of concern (VOC), the Omicron variant (B.1.1.529). Their survival was examined on plastic (polystyrene plate) surfaces and human skin samples collected from autopsies. Survival time was the time until the viral titer could no longer be detected on the surface.

All the four VOCs showed more than two-fold longer survival times on both the surfaces tested.

The survival period of Omicron on plastic was found to be 193.5 hours amounting to 8.06 days. The delta variant survived for 114 hours, alpha for 191.3 hours, beta for 156.6 hours and Gamma for 59.3 hours. The original Wuhan strain was found to survive for 56 hours.

Comparison of survival time on skin samples showed a survival time of 21.1 hours for the Omicron variant compared to 16.8 hours for Delta. The alpha variant survived for 19.6 hours, beta for 19.1 hours and gamma for 11 hours. The original virus strain was found to survive for 8.6 hours.

The effectiveness of alcohol-based disinfectants against these VOCs was also studied. All strains were completely inactivated after exposure to 35% ethyl alcohol for 15 seconds. Hence, alcohol-based hand sanitizers containing at least 60% ethyl alcohol, as recommended by the WHO, should be used regularly for hand cleaning.

The Omicron variant was first identified in November last year. Since then, it has swiftly replaced the delta variant to become the dominant strain globally. The prevalence of delta is declining, with limited circulation of Alpha, Beta and Gamma variants. The highly transmissible nature of Omicron is attributed to its immune evading properties and its propensity for the upper respiratory tract instead of the lungs. The greater environmental stability as shown in this preprint study may also be a factor contributing to its rapid spread.

Reference

1. Ryohei Hirose, et al. Differences in environmental stability among SARS-CoV-2 variants of concern: Omicron has higher stability. bioRxiv, posted January 19, 2022. doi: https://doi.org/10.1101/2022.01.18.476607.