Another pre-print is out looking at #SARSCoV2 #HCoV19 #COVID19 #coronavirus stability in different environmental conditions. (Thanks, @DocBazac, for the tip!)
medrxiv.org
medrxiv.org
This preprint looked at the effect of temperature. Bad news: in virus transport medium, infectious titer (amount of infectious virus), was pretty stable, with <1 log reduction over 14 days at 4 degrees C. (4 C is the temperature of your refrigerator)
However, it confirmed that heat can inactivate the virus. When temperature was increased to 70 C, the virus was inactivated in 5 minutes. This has implications for disinfection methods and may be especially relevant for reusing PPE.
In this study, the ambient conditions were room temp (22 C) with 65% relative humidity (that's fairly high). Under these conditions, no infectious virus on printer or tissue paper could be recovered after 3 h. On treated wood or cloth, no virus could be recovered after 2 days.
The authors assert that surface textures are important. Under these conditions, no infectious virus could be recovered from glass or paper currency after day 4 or plastic/stainless steel after day 7.
(Aside: not sure if the bank notes tested were HKDs fresh from the mint. I wouldn't go so far to say that the USDs in my wallet are "smooth" surfaces. This could have an impact on the risk presented by handling money, but it's hard to say what that is. Keep washing those hands!)
For all the mask-lovers out there: 0.1% of the inoculum could be detected on a surgical mask after a week. The inoculum was ~600K TCID50/mL (units of the dose required to kill 50% of the Vero E6 cells in a tissue culture dish per milliliter). That's 600 TCID50/mL.
We don't know what the minimum infectious dose is for people (the minimum # of infectious units needed to infect a human), but 600 TCID50/mL after a week suggests that infectious virus can at least persist on surgical masks for a week. Thus masks are a potential exposure risk.
The virus also was stable over a broad range of pH, meaning that it's more tolerant to both acidic (low pH) and basic (high pH) conditions. The good news is that they also tested disinfectants, which were all very effective in inactivating virus in short periods of time.
A note of caution: this is a preprint so it hasn't undergone peer review. However, it is from Malik Peiris and Leo Poon's groups, and they are highly regarded virologists who were the first to isolate SARS classic and have extensive experience studying coronaviruses.
The take-home is that SARS-CoV-2 is stable on many surfaces, including surgical masks, for days under specific environmental (temp/humidity) conditions. The virus is sensitive to changes in temperature and can be inactivated rapidly by disinfectants, just like other coronaviruses
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