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

Abstract

Decontamination of objects and surfaces can limit transmission of infectious agents via fomites or biological samples. It is required for the safe re-use of potentially contaminated personal protective equipment and medical and laboratory equipment. Heat treatment is widely used for the inactivation of various infectious agents, notably viruses. We show that for liquid specimens (here suspension 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 37.0 min ([12.65, 869.82]) in uncovered plates in a dry oven. These findings suggest a critical role of evaporation in virus inactivation using dry heat. Placing samples in open or uncovered containers may dramatically reduce the speed and efficacy of heat treatment for virus inactivation. Heating procedures must be carefully specified when reporting experimental studies to facilitate result interpretation and reproducibility, and carefully considered when designing decontamination guidelines.

Methods to disinfect and decontaminate SARS-CoV-2: a systematic review of in vitro studies

“…A total of 27 studies were included in this review after screening and reviewing potentially relevant studies (as shown in Figure 1 ). 5 – 31 …”

Biosafety during a pandemic: shared resource laboratories rise to the challenge

“…The ability of an SRL to rapidly respond to the emergence of a new pathogen centers on having established biological safety assessment procedures in place (3, 25, 34), along with a human risk assessment (Appendix). At this time, literature is starting to form a consensus around the stability and inactivation of SARS‐CoV‐2 (14, 16–18, 38–40, 43–45, 50). Exactly how these inactivation methods are applied in SRLs will relate directly to the sample type and the level of risk posed.…”

“…Fixation is often performed with the primary goal of stabilizing samples for downstream assays (e.g., intracellular staining). However, fixation protocols designed for stabilization may not necessarily result in pathogen inactivation and special care is needed in the assessment and development of fixation protocols (14, 26, 34–45). Commercial products, both within and across companies, often contain varying concentrations of fixative.…”

“…Viral inactivation validation protocols can be found in these references (15–18, 40, 44, 46–50). In all fixation protocols, it is imperative to consider the: (1) fixative used; (2) how fresh this fixative is; (3) the concentration of the fixative; (4) the time of incubation; and (5) the temperature maintained during incubation (40, 42, 43, 47, 49). Critically, it has been demonstrated in a number of publications that fixation at low temperatures, for example at 4°C, often results in insufficient inactivation of pathogens (42, 43, 47, 49).…”

“…Incorporating a fixation protocol into the preparation of samples is a procedure familiar to many users, making this a straightforward process for controlling risk.Fixation is often performed with the primary goal of stabilizing samples for downstream assays (e.g., intracellular staining). However, fixation protocols designed for stabilization may not necessarily result in pathogen inactivation and special care is needed in the assessment and development of fixation protocols(14,26,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45). Commercial products, both within and across companies, often contain varying concentrations of fixative.…”