#18,306
While the public health impact from COVID has diminished greatly since the pre-vaccine days of 2020, it continues to reinvent itself into new variants, and produce new waves of infection, which sicken tens of thousands of people every day.. . . during the 28-day period (22 July to 18 August 2024), the number of new cases and deaths increased by 23% and 44% compared to the previous 28-day period (24 June to 18 August 2024), with 238 000 new cases reported across 91 (39%) countries and about 4400 new fatalities reported across 35 (15%) countries, respectively.
Given that the vast majority of nations no longer report cases or deaths to the WHO, actual numbers are almost certainly several times higher.
While we may wish to be through with COVID, the virus is obviously far from through with us.
Nearly 5 years into this public health crisis, there are still unanswered questions about how SARS-CoV-2 (and likely other similar coronaviruses) transmit in the real world.
Fomites, or inanimate objects (doorknobs, desktops, hospital bed rails, even money) were initially viewed as major conveyors of the virus, and tests were run to determine how long the virus could remain viable on various surfaces (see EID Journal: Prolonged Infectivity of SARS-CoV-2 in Fomites).While fomite transmission almost certainly occurred, over time it became evident that respiratory droplets and aerosols were the primary driver of the pandemic.
Today we have a preprint which finds that SARS-CoV-2 transfers better from non-porous surfaces (like glass, plastic, or steel) than porous surfaces (like cardboard), and that it can remain infectious on the skin for hours or even days.
First, the link, abstract, and some excerpts from the preprint, after which I'll have a brief postscript.
SARS-CoV-2 Survival on Skin and its Transfer from Contaminated Surfaces
Ana Karina Pitol Garcia, Samiksha Venkatesan, Siobhan Richards, Michael Hoptroff, Amitabha Majumdar, Grant Hughes
doi: https://doi.org/10.1101/2024.09.18.613660
Abstract
Understanding the transmission dynamics of SARS-CoV-2, particularly its transfer from contaminated surfaces (fomites) to human skin, is crucial for mitigating the spread of COVID-19. While extensive research has examined the persistence of SARS-CoV-2 on various surfaces, there is limited understanding of how efficiently it transfers to human skin, and how long it survives on the skin.
This study investigates two key aspects of SARS-CoV-2 transmission: (1) the transfer efficiency of SARS-CoV-2 from non-porous (plastic and metal) and porous (cardboard) surfaces to a 3D human skin model (LabSkin), and (2) the survival of SARS-CoV-2 on the skin under different temperature conditions.
First, we validated LabSkin as a suitable surrogate for human skin by comparing the transfer efficiency of the bacteriophage Phi 6 from surfaces to LabSkin and to human volunteers fingers. No significant differences were observed, confirming LabSkin's suitability for these studies.
Subsequently, the transfer of SARS-CoV-2 from surfaces to LabSkin was assessed, showing that plastic and metal surfaces had similar transfer efficiencies (~13%), while no transfer occurred from cardboard once the inoculum had dried on the surface.
Finally, the survival of SARS-CoV-2 on skin was assessed, showing a rapid decay at higher temperatures, with a half-life ranging from 2.8 to 17.8 hours depending on the temperature. These findings enhance our understanding of viral transmission via fomites and inform public health strategies to reduce the risk of SARS-CoV-2 transmission through surface contact.
(SNIP)
In addition to assessing virus transfer, our study demonstrates that SARS-CoV-2 can remain infectious on human skin for hours to days, with its survival significantly influenced by temperature. Specifically, we observed that higher temperatures result in reduced viral half-lives, which aligns with existing literature indicating lower survival rates of SARS-CoV-2 at elevated temperatures (7,9,14,43).
The impact of temperature on the persistence of viruses, including SARS-CoV-2, across various surfaces, food, skin, and other environmental reservoirs has been documented in numerous studies (51,52). These studies consistently show that higher temperatures accelerate the decay of infectious virus. Furthermore, temperature is just one of several environmental factors, including humidity and UV exposure, that can significantly alter virus stability and its transmission in different contexts (52,53)
(SNIP)
In conclusion, this study provides important insights into the mechanisms of SARS-CoV-2 transmission via surfaces and its subsequent survival on human skin. By validating the use of a 3D human skin model, LabSkin, as a surrogate for actual human skin, we were able to accurately quantify virus transfer from various surfaces and assess its survival on the skin over time.Our findings suggest that non-porous surfaces, such as plastic and metal, facilitate greater virus transfer compared to porous surfaces like cardboard, where the virus rapidly penetrates the material, making the recovery of infectious virus infeasible within minutes. Additionally, we found that SARS-CoV-2 can persist on human skin for significant periods, with higher temperatures accelerating viral decay.These findings underscore the complexity of virus transmission dynamics and emphasize the critical role of environmental factors in influencing virus survival. While our study advances the understanding of these processes, it also points to the necessity for further research into how other environmental variables, such as humidity and the state of the virus inoculum, and transfer parameters such as contact pressure and contact friction may affect virus transmission in everyday settings.
With fall approaching, and temperatures dropping, the risks of transfer of SARS-CoV-2 from fomites is likely to increase.
While hand-washing or sanitizing shouldn't be your only line of defense during a respiratory virus outbreak, it certainly has a place in a multi-pronged NPI (non-pharmaceutical intervention) strategy.
Although this study deals specifically with SARS-CoV-2, we've also looked at the environmental persistence of H5N1. A few past blogs include:
EID Journal: Persistence of Influenza H5N1 and H1N1 Viruses in Unpasteurized Milk on Milking Unit Surfaces
Viruses: Assessment of Survival Kinetics for Emergent Highly Pathogenic Clade 2.3.4.4 H5Nx Avian Influenza Viruses
Environmental Surveillance and Detection of Infectious HPAI Virus in Iowa Wetlands
Emerg. Microbes & Inf.: Feather Epithelium Contributes to the Dissemination and Ecology of clade 2.3.4.4b H5 HPAI Viruses in Ducks
