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Aerosol and surface stability of SARS-CoV-2 compared to SARS-CoV-1 [pdf] (medrxiv.org)
53 points by cycop 26 days ago | hide | past | web | favorite | 42 comments

I think the important result of this study is that HCov-19 has essentially the same half life on every surface they tested as SARS-CoV-1 except cardboard. "In general, there was no statistically discernable difference in half-life between the two viruses on any given surface except for cardboard: all other 95% credible intervals for the difference in half-lives overlapped 0".

Importantly, "Our results indicate that the greater transmissibility observed for HCoV-19 is unlikely to be due to greater environmental viability of this virus compared to SARS-CoV-1."

Edit: Remove line number from copy and pasted quote. Also fixed SARS virus name.

I just want to stress this again!

I see so many people claiming that you need to quarantine your packages for X days to be safe - this does not seem to be what the study says!

That doesn't seem to be true unless the number of particles they spread on the surfaces is representative of someone handling a package with contaminated hands.

Viral particles seem to decay exponentially with a specific half-life (the environment just seems to break them down/inactivate and it's essentially a random process). So if you start with many more viral particles than this study, then more infectious viral particles will be on the surface after a set amount of time. Viruses do not seem to be like cells with a specific "life-time".

This study essentially shows that this virus behaves a lot like SARS-CoV-1 but spreads more aggressively - it must be something other than longer viability on surfaces/aerosols.

Can someone please explain if there's some semi-obvious subtext to the caveat -- that greater comparative transmissibility is NOT due to comparative longevity on surfaces.

Is there something else specifically, or is this just a general observation that greater transmissibility must be due to 'some other factor(s)'?

The longevity is exactly the same, therefore it is likely that the greater transmissibility is due to a different factor. I think that's the only reasoning that's going on.

Latency and silent cases is probably enough.

you mean SARS-CoV-1 in the first para

Yes, I do. Thanks. Edited.

About the same range as influenza, which is thought to be about 48 hours, but significantly longer than most common cold viruses, which remain active for only a few hours at most.

Validates the Chinese approach of essentially banning doorhandles - jam doors open, and for those that can't be jammed, wrap them in cloth covered in disinfectant.

I wish designers can now go with a kick button, that will allow you to open the door.

Put the kick button a few inches off the floor, so anyone can easily kick it, and it activates a mechanical arm that swings open the door for you. Mount it on the wall next to the door, and of course, you will need two, one on each side of the door.

Aside: this paper demonstrates an interesting use of Bayesian regression to get the full posterior distribution over plausible decay rates rather than just a single point estimate. See the last few pages.

Is this pretty normal in these sorts of papers?

That means any items you buy in a supermarket (greens wrapped in plastic, toilet paper, packaged meet, tin cans) should be set aside at home for 3 days? And you need to disinfect yourself after each round to the store...

Just don't lick the plastic your toilet paper comes wrapped in, unpack it when you get home, and wash your hands. Same with trips to the store. This calls for being a bit more conscious of basic hygiene, not showering in disinfectant.

No, not as far as I can tell.

If I read this paper right, viruses on surfaces/aerosols decay exponentially (so no specific "life-time") and they determined the half-lives here. Start with more particles and you reach the detection threshold later.

To figure out when all viral particles are inactive you'd have to know how many particles you'd typically start with. I doubt that the amount of particles they spread on the surfaces is typical of what an infected person would spread.

You could wipe them with a disinfectant wipe. Or wash your hands. Or both.

correct. also quarantine deliveries.

Could i use commercial UV-lights (like for tanning or medicinal appliance) and illuminate the items to kill off the virus?

Good question. I suspect viruses are less UV-sensitive than bacteria

However the main issue is that protecting yourself from the UV blast might be more complicated than just disinfecting the product using traditional means

It looks like we can now get COVID-19 from Amazon Prime. Free 2-day delivery for all!

A tired warehouse worker, forced to work overtime by Jeff Bezos, with no health insurance or paid sick time, and with a robot that watches his every move to make sure he isn’t slacking, gets sick with the virus, and sneezes on your order. The package gets delivered to you in 2 days, and you open it up, and hold it in your hands, thinking the product is clean and sterile. Then 3 days later, you get a strange cough, then the next day, you develop a high fever. Boom! You just got infected with COVID-19.

It didn’t come from China, but from your friendly (and sick) Amazon warehouse worker.

Perhaps it's a good idea to place copper tape on all door handles and other frequently touched objects. It's certainly very cheap to do so. Here's some discussion on that idea with more evidence: https://www.lesswrong.com/posts/LwcKYR8bykM6vDHyo/coronaviru...

Silver could be even better. (including nanosilver coating as used in some food processing hardware such as refrigerators)

> Caution: Preprints are preliminary reports of work that have not been peer-reviewed. They should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.

Now I really hope this report turns out to be flawed.

So do I, but it still seems prudent to act like it is true: The extra hygiene measures are a very minor inconvenience, especially compared to the major inconvenience of catching the virus.

If I have to be hospitalized, and nobody should enter my apartment for three days to take care of my cats, and it turns out it’s unwarranted, that’s a big inconvenience for me.

Get an auto feeder for food and water that can feed your cats when you are not around for 5-6 days.

this has been studied already in china but the rest of the world ignores. https://www.scmp.com/news/china/science/article/3074351/coro...

I like to think of it as, the US is one big cruise ship but with coronavirus instead of norovirus.

Reading that the virus is stable in the air for 3h, you would think that the R0 would be closer to measles, i.e. ~18 instead of ~2. Any ideas why this is not the case?

Lack of symptoms in many more cases, for longer time. If measles had no symptoms for a week, it'd spread way more easily.

The half life estimate is more interesting. 13hours on steel. 16 for plastic.

Is it? Don't all viruses die after a more or less fixed timespan? Do they decay like radioactive elements?

If viruses died at a fixed timespan, I think that would point to there being a stateful element that keeps track of elapsed time, like a molecular sand timer.

If viruses die because of spontaneous reactions, eg interaction with surfaces, interactions with photons, or a spontaneous chemical reaction like oxidation, then I would expect half-life decay similar to radioactive elements.

I don't know how viruses die. I wonder if they can be preserved near indefinitely in a non reactive gas or vacuum in the dark.

Why weren't other materials tested? Brick, concrete, woods?

What is the temperature (room temperature) during the test?

21-23 degrees Celcius, 63% humidity

Has anyone considered the probability of the virus spreading via overnight e-commerce packages inadvertently containing infected steel/plastic?

Don’t many overnight packages go through some really cold (warehouse/flight) or really hot (desert trucking) scenarios? I imagine it’s mostly viable in comfortable human conditions

It is my understanding that viruses tend to enjoy cold, and the temperatures aren't deep enough to kill them.

Also why don't we say virii anymore?

Because loan words tend to get adapted to the grammar of the host language with time?

Virii was never in. I've never heard of computer "virii".

I have received a packet from Milano yesterday (when I ordered, it wasn't clear that the senders logistics center apparantly is in Italy) and used lots of hand sanitizer while opening. It's nice to see these numbers now, indicating that this probably wasn't necessary for a packet that took a week or so to arrive.

non-zero. safest to assume it is present and quarantine it for 3 days before handling.

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