As winter is lashing the northern hemisphere, public health officials are apprehensive as to how the seasonal shift will impact the spread of SARS-CoV-2, the virus that causes COVID-19. A study of individual particle degradation of coronavirus confirms a potential surge of COVID-19 infections in the winter.
The study tested how temperatures and humidity affect the structure of individual SARS-Cov-2 virus-like particles on surfaces and found that just moderate temperature increase has brokedn down the virus' structure, while humidity had very little impact.
To survive, the SARS-Cov-2 membrane needs a specific web of proteins arranged in a particular order and when it falls apart, it becomes less infectious. The findings suggest that in winter when temperatures drop, coronavirus remains infectious longer.
This is the first study to analyze the mechanics of the virus at an individual particle level, but the findings agree with large-scale observations of other coronaviruses that appear to infect more during the winter months.
"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," said Michael Vershinin, assistant professor at the University of Utah and co-senior author of the paper. "What's surprising is how little heat was needed to break them down--surfaces that are warm to the touch, but not hot. The packaging of this virus is very sensitive to temperature."
The paper, published recently in the journal Biochemical Biophysical Research Communications and as a separate paper in Scientific Reports, describes 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.
Spreads by sneezing or coughing
The SARS-CoV-2 is commonly spread by sneezing or coughing, ejecting droplets of tiny aerosols from the lungs. These mucus 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.
When researchers 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 found to be stronger on the dry particles than on the liquid ones. In contrast, surfaces at about 71 degrees F caused little to no damage, suggesting that particles in room temperature or outside in cooler weather will remain infectious longer.
They saw very little difference under levels of humidity on surfaces, though they stress that humidity does matter when the particles are in the air, by affecting how fast the aerosols dry out.
"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," Vershinin said. This new method allows scientists to experiment with any virus without risking an outbreak.
