With the arrival of winter, public health officials are asking how the seasonal shift will impact the spread of SARS-CoV-2, the virus that causes COVID-19. A new study from scientists at the University of Utah may provide an answer.
The study tested how temperatures and humidity affect the structure of individual SARS-Cov-2 virus-like particles on surfaces. Scientists 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. 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.
“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 UofU 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 was published online on Nov. 28, in the journal Biochemical Biophysical Research Communications. The team also published a separate paper on Dec. 14 in Scientific Reports describing their method for making the individual particle packaging. 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.
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 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. Tested on glass surfaces, scientists elevated the temperature to about 93 degrees F for 30 minutes, which 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.
“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. “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.”