Thermal Inactivation of Aerosolized SARS-CoV-2

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide with its different variants. The transmission efficiency of the new variants is much higher than the existing ones. Therefore, developing new preventive measures based on the transmission routes of the virus is needed to limit the spread. The possible transmission routes include direct contact with surfaces contaminated with droplets secreted by patients and airborne viral transmission from person to person. Thermal inactivation is a preventive measure that applies high temperature to objects or fluids, as has been reported previously. However, inactivation data of aerosolized SARS-CoV-2 exposed to heat for a short time at high temperatures are not in the literature yet. We evaluated the inactivation of the aerosolized virus while passing through an electric heater. The virus inactivation test experiments were conducted at two temperatures of the heater’s outlet air, 150±5 o C, and 220±5 o C, at an air flow rate of 0.6 m 3 /h (10 L/min) and heat exposure time of 1.44 s. The loss in viability of the virus at 150 o C and 220 o C was measured as 99.900% and 99.999%, respectively. The results indicate that the high-temperature inactivation of SARS-CoV-2 may potentially reduce aerosolized viral indoors.

SARS-CoV-2 is rapidly inactivated at high temperature

In the absence of a vaccine, preventing the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the primary means to reduce the impact of the 2019 coronavirus disease (COVID-19). Multiple studies have reported the presence of SARS-CoV-2 genetic material on surfaces suggesting that fomite transmission of SARS-CoV-2 is feasible. High temperature inactivation of virus has been previously suggested, but not shown. In the present study, we investigated the environmental stability of SARS-CoV-2 in a clinically relevant matrix dried onto stainless steel at a high temperature. The results show that at 54.5 °C, the virus half-life was 10.8 ± 3.0 min and the time for a 90% decrease in infectivity was 35.4 ± 9.0 min. These findings suggest that in instances where the environment can reach temperatures of at least 54.5 °C, such as in vehicle interior cabins when parked in warmer ambient air, that the potential for exposure to infectious virus on surfaces could be decreased substantially in under an hour.

Inactivating porcine coronavirus before nuclei acid isolation with the temperature higher than 56 °C damages its genome integrity seriously

Abstract2019-Novel Coronavirus (2019-nCoV) is the pathogen of Corona Virus Disease 2019. Nucleic acid detection of 2019-nCoV is one of the key indicators for clinical diagnosis. However, the positive rate is only 30-50%. Currently, fluorescent quantitative RT-PCR technology is mainly used to detect 2019-nCoV. According to “The Laboratory Technical Guidelines for Detection 2019-nCoV (Fourth Edition)” issued by National Health and Commission of China and “The Experts’ Consensus on Nucleic Acid Detection of 2019-nCoV” released by Chinese Society of Laboratory Medicine, the human samples must be placed under 56°C or higher to inactivate the viruses in order to keep the inspectors from virus infection before the nucleic acids were isolated as the template of qRT-PCR. In this study, we demonstrated that the virus inactivation treatment disrupts its genome integrity seriously when using porcine epidemic diarrhea virus (vaccine), a kind of coronavirus, as a model. Our results showed that only 50.11% of the detectable viral templates left after the inactivation of 56 °C for 30 minutes and only 3.36% left after the inactivation of 92 °C for 5 minutes when the samples were preserved by Hank’s solution, one of an isotonic salt solutions currently suggested. However, the detectable templates of viral nucleic acids can be unchanged after the samples were incubated at 56 °C or higher if the samples were preserved with an optimized solution to protect the RNA from being disrupted. We therefore highly recommend to carry out systematic investigation on the impact of high temperature inactivation on the integrity of 2019-nCoV genome and develop a sample preservation solution to protect the detectable templates of 2019-nCoV nucleic acids from high temperature inactivation damage.