Coronavirus News: Study Shows That SARS-CoV-2 Virus Like Particles Highly Sensitive To Temperature Increases And Thrives In Cool Temperatures
: A new study by researchers from the University of Utah and the University of California-Davis shows that SARS-CoV-2 coronavirus like particles are highly sensitive to temperature increases and thrives in cooler temperatures.
The SARS-CoV-2 is a novel coronavirus which has caused the COVID-19 pandemic. Other known coronaviruses show a strong pattern of seasonality, with the infection cases in humans being more prominent in winter.
Though several plausible origins of such seasonal variability have been proposed, its mechanism is unclear. SARS-CoV-2 is transmitted via airborne droplets ejected from the upper respiratory tract of the infected individuals. It has been reported that SARS-CoV-2 can remain infectious for hours on surfaces. As such, the stability of viral particles both in liquid droplets as well as dried on surfaces is essential for infectivity.
In this study, the researchers have used atomic force microscopy to examine the structural stability of individual SARS-CoV-2 virus like particles at different temperatures.
The study team demonstrates that even a mild temperature increase, commensurate with what is common for summer warming, leads to dramatic disruption of viral structural stability, especially when the heat is applied in the dry state. This is consistent with other existing non-mechanistic studies of viral infectivity, provides a single particle perspective on viral seasonality, and strengthens the case for resurgence of COVID-19 in winter.
The study findings were published in the peer reviewed journal: Biochemical Biophysical Research Communications https://www.sciencedirect.com/science/article/pii/S0006291X20321239
With winter fast approaching in the northern hemisphere, public health officials are asking how the seasonal shift will impact the spread of SARS-CoV-2, the virus that causes COVID-19?
The study team tested how temperatures and humidity affect the structure of individual SARS-Cov-2 virus-like particles on surfaces. The team found that just moderate temperature increases broke down the virus' structure, while humidity had very little impact. In order to remain infectious, the SARS-Cov-2 membrane needs a specific web of proteins arranged in a particular order.
However when that structure falls apart, it becomes less infectious. The findings suggest that as temperatures begin to drop, particles on surfaces will remain infectious longer.
To date, this is the first study to analyze the mechanics of the virus on an individual particle level, but the findings agree with large-scale observations of other coronaviruses that appear to infect more individuals during the winter months.
Dr Michael Vershinin, assistant professor at the University of Utah and co-senior author of the paper told Thailand Medical News, "You would expect that temperature makes a huge difference, and that's what we saw. To the point where the packaging of the virus was completely destroyed by even moderate temperature increases.”
He added, "What's surprising is how little heat was needed to b
reak them down ie surfaces that are warm to the touch, but not hot. The packaging of this virus is very sensitive to temperature."
The study team also published a separate paper Dec. 14, 2020 in Scientific Reports describing their method for making the individual particle packaging. https://www.nature.com/articles/s41598-020-78656-w
Basically the virus-like particles are empty shells made from the same lipids and three types of proteins as are on an active SARS-Cov-2 viruses, but without the RNA that causes infections. This new method allows scientists to experiment with the virus without risking an outbreak.
It is already known that the SARS-CoV-2 is commonly spread by exhaling sharply, (e.g. sneezing or coughing), which ejects droplets of tiny aerosols from the lungs. These mucus-y droplets have a high surface to volume ratio and dry out quickly, so both wet and dry virus particles come into contact with a surface or travel directly into a new host. The researchers mimicked these conditions in their experiments.
The study team tested the virus-like particles on glass surfaces under both dry and humid conditions. Using atomic force microscopy they observed how, if at all, the structures changed. The scientists exposed samples to various temperatures under two conditions: with the particles inside a liquid buffer solution and with the particles dried out in the open. In both liquid and bare conditions, elevating the temperature to about 93 degrees F for 30 minutes degraded the outer structure.
The effect was stronger on the dry particles than on the liquid-protected ones. In contrast, surfaces at about 71 degrees F caused little to no damage, suggesting that particles in room temperature conditions or outside in cooler weather will remain infectious longer.
The study team saw very little difference under levels of humidity on surfaces, however the scientists stress that humidity likely does matter when the particles are in the air by affecting how fast the aerosols dry out. The research team is continuing to study the molecular details of virus-like particle degradation.
Dr Vershinin added, "When it comes to fighting the spread of this virus, you kind of have to fight every particle individually. And so you need to understand what makes each individual particle degrade. People are also working on vaccines and are trying to understand how the virus is recognized? All of these questions are single particle questions. And if you understand that, then that enables you to fight a hoard of them."
The study team concluded,”The unexpected finding is how little heating it takes to degrade VLPs or virus like particles ie just 34 °C was sufficient for a dramatic effect. Surfaces at 34 °C are warm to the touch but not hot. Such conditions are likely widespread in many locales for outdoors surfaces. In contrast,
surfaces at 22 °C do not promote rapid VLP degradation, suggesting that surfaces commonly found indoors and the surfaces located outdoors during colder seasons may allow for prolonged viral survival and possibly extended viral spread. It is hard to estimate how all individual contributing factors would contribute to the epidemiological picture on the ground. Nonetheless, our findings draw parallels between the stability of SARS-CoV-2 and the original SARS viruses and add to a growing body of research suggesting more viral spread is likely at lower temperatures via a variety of possible contributing factors.”
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