Using heat to kill SARS‐CoV‐2

 John P. Abraham, 1 Brian D. Plourde, 1 and Lijing Cheng 2

doi: 10.1002/rmv.2115 [Epub ahead of print]

PDF: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7361064/pdf/RMV-9999-e2115.pdf

Summary

The current coronavirus pandemic has reached global proportions and requires unparalleled collective and individual efforts to slow its spread. One critically important issue is the proper sterilization of physical objects that have been contaminated by the virus. Here, we review the currently existing literature on thermal inactivation of coronavirus (SARS‐CoV‐2) and present preliminary guideless on temperatures and exposure durations required to sterilize. We also compare these temperatures/exposure durations with potential household appliances that may be thought capable of performing sterilization.

1.2. Recommendations for thermally destroying coronavirus

We provide a reasonable estimate for near complete thermal destruction of coronavirus. For temperatures above 65°C (149°F) is expected to cause near complete inactivation with exposures greater than 3 minutes. For temperatures between 55 and 60°C (131‐140°F) heating should last 5 minutes or more. However, for temperatures in the range 50‐55°C (122‐131°F) we recommend 20 minutes or longer of exposure. At these levels, we expect the viral concentration to be lowered by log 5‐7, near or below the detectable limit.

Because of the seriousness of the current coronavirus infection, we suggest a reasonable safety factor can be obtained by increasing the above‐listed temperatures by 10°C (about 18 °F). Extensive research has confirmed that at least for living cells, the sensitivity of thermal destruction is very strongly linked to temperature. That is, small increases in temperature cause large increases in the death rate. As an example, for mammalian cells and other pathogens (bacteria, viruses, and protozoa) the death rate rises rapidly as temperature increases. 7 , 8 Another reason for using a safety factor is that the temperatures experienced by the virus during heating will not necessarily equal the temperature of the applied heat. Thermal inertia causes a heating lag that depends, in part, on the media being heated.

With this conservative approach, the following become the recommendations:

In order to kill COVID‐19, heat virus‐containing objects for:

• 3 minutes at temperature above 75°C (160°F).

• 5 minutes for temperatures above 65°C (149°F).

• 20 minutes for temperatures above 60°C (140°F).

It should be noted that these findings agree with WHO guidelines which report a 4 log reduction of coronavirus for 56°C (133°F) with 15‐minute exposures 14 and is consistent with information for killing other infectious agents. 15

These recommendations are hotter than encountered in residential clothes dryers, clothes washing machines, and dish washers. For these appliances, temperatures are typically at or below 57°C (135°F). These temperatures are also much hotter than residential hot water (in the United States), for example, plumbing codes limit hot water to 49°C (120°F).

Of course, since soap has some virucide characteristics, washing with soap is expected to inactivate viruses by nonthermal means.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7361064/