Heat-treated virus inactivation rate depends strongly on treatment procedure: illustration with SARS-CoV-2

Abstract Decontamination can limit environmental transmission of infectious agents. It is required for the safe re-use of contaminated medical, laboratory and personal protective equipment, and for the safe handling of biological samples. Heat is widely used for inactivation of infectious agents, notably viruses. We show that for liquid specimens (here, solution of SARS-CoV-2 in cell culture medium), virus inactivation rate under heat treatment at 70°C can vary by almost two orders of magnitude depending on the treatment procedure, from a half-life of 0.86 min (95% credible interval: [0.09, 1.77]) in closed vials in a heat block to 37.00 min ([12.65, 869.82]) in uncovered plates in a dry oven. These findings suggest a critical role of evaporation in virus inactivation via dry heat. Placing samples in open or uncovered containers may dramatically reduce the speed and efficacy of heat treatment for virus inactivation. We conducted a literature review focused on the effect of temperature on coronavirus stability and found that specimen containers, and whether they were closed, covered or uncovered, are rarely reported in the scientific literature. Heat-treatment procedures must be fully specified when reporting experimental studies to facilitate result interpretation and reproducibility, and carefully considered when designing decontamination guidelines. Importance Heat is a powerful weapon against most infectious agents. It is widely used for decontamination of medical, laboratory and personal protective equipment, and for biological samples. There are many methods of heat treatment, and methodological details can affect speed and efficacy of decontamination. We applied four different heat-treatment procedures to liquid specimens containing SARS-CoV-2. The results reveal an important effect of the containers used to store specimens during decontamination: for a given initial level of contamination, decontamination time can vary from a few minutes in closed vials to several hours in uncovered plates. Reviewing the literature, we found that container choices and heat treatment methods are rarely made explicit in methods sections. Our study shows that careful consideration of heat-treatment procedure—in particular the choice of specimen container, and whether it is covered—can make results more consistent across studies, improve decontamination practice, and provide insight into the mechanisms of virus inactivation.