A severe shortage of personal protective equipment resulting from the surge in hospitalizations at the onset of the COVID-19 pandemic left medical workers searching for safe methods to decontaminate disposable masks and other equipment and wondering whether dry heat would be effective. Meanwhile, epidemiologists struggled to reach a consensus on the impact of environmental temperature on the transmission of COVID-19 because statistical analyses are typically limited to specific regions and often influenced by many other environmental factors. To provide insight into these issues, we developed a thermodynamic modeling framework constructed from the rate law and Arrhenius equation that describes the inactivation rate of viruses as a function of temperature. We validated this model with experimental data obtained for the thermal inactivation of SARS-CoV-2 at four temperatures (25 °C, 40 °C, 55 °C, and 70 °C) and found that, while SARS-CoV-2 remains viable for hundreds of hours at room temperature, low-grade dry heat can inactivate the virus within minutes. Furthermore, characterization using scanning electron microscopy, X-ray photoelectron spectroscopy, and water contact angle goniometry revealed that delicate polypropylene masks do not experience physical or chemical degradation upon exposure to low-grade heat. We also applied our model to environmental temperatures and found that (i) higher mean environmental temperatures and (ii) higher ranges of daily temperature fluctuations both resulted in a shorter SARS-CoV-2 lifetime, in apparent agreement with early statistical epidemiological studies on the spread of COVID-19. This modeling framework provides a new understanding of the thermal inactivation of viruses as a function of temperature that applies not only to SARS-CoV-2, but also a range of other endemic viruses and, potentially, yet-unencountered novel viruses.

Reaction kinetics governing the thermal inactivation of viruses

ACS Fall 2021

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