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Comment by tzs | Hacker News Reader

Slightly OT: numerous sources say that if the virus is on a surface, it eventually dies (or deactivates anyway, if you don't consider viruses alive in the first place). It can last up to 4 days on glass, 3 on steel and plastic, and 24 hours on cardboard.

What I've not seen explained and have no guess for is why it deactivates. It doesn't have a metabolism. It doesn't consume resources or use energy. It just sits there, a little spiky spheroid surrounding some fragments of DNA or RNA.

So what changes about it as it sits that causes it to deactivate?

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https://www.marketwatch.com/story/deadly-viruses-are-no-matc...

So why are surfaces different? The virus is held together by a combination of hydrogen bonds (like those in water) and hydrophilic, or “fat-like,” interactions. The surface of fibers or wood, for instance, can form a lot of hydrogen bonds with the virus.

In contrast, steel, porcelain or Teflon do not form much of a hydrogen bond with the virus. So the virus is not strongly bound to those surfaces and is quite stable.

I linked Thordarson's Twitter thread on the subject above. Didn't know he'd written an article too. Nice!

They dry out.

https://www.usatoday.com/in-depth/news/2020/03/25/coronaviru...

> In all settings, viruses need water to survive. "Viruses can withstand a small amount of dehydration," says Dr. Paul Meechan, a former director of safety at the Centers for Disease Control and Prevention and president of the American Biological Safety Association.

I believe this is the correct answer. My daughter with the masters in biology also said this was the answer.

Interesting side effect is that you can deactivate the virus by putting it in a warm dry atmosphere. The warmth encourages evaporation and drying.

Sadly I don't have any equipment for doing viral particle counts (was tempted to bid on some here: https://www.equipnet.com/auctions/ but alas, I already have way more EE test gear than I can use, no sense adding a full bio laboratory to the mix :-).

Even though I cannot prove its viability as a mitigation solution, since I have a heat gun I spray my mail with 610 degree F heat to ensure it is dry and warm (without exceeding 452 degrees of course!)

I'm curious to see how the curve might be affected with warmer weather coming to the northern hemisphere.

One can hope, certainly in the drier climates. As challenging as the pandemic is, the science part is still fascinating to me.

the corona virus (similar to the HI virus) has an envelope which is a lipid bilayer, there are viruses without an envelope. Now you may think that a virus with an envelope is more stable than viruses without, but the contrary is the case. once the bilayer tears, the virus is dysfunctional.

Also, what is not always talked about in the media currently is, that not all viruses are replicated functional. In fact, a large fraction of viruses produced are not capable of infecting a cell in the first place due to replication errors, mutations, etc.

>what is not always talked about in the media currently is, that not all viruses are replicated functional. In fact, a large fraction of viruses produced are not capable of infecting a cell in the first place due to replication errors, mutations, etc.

I agree that people aren't writing news articles about that, but why is it noteworthy that they're not? It doesn't matter if only 1% of the virus particles on a surface are infectious if there are millions of particles.

Entropy. A virus is simple by the standards of living things, but it's still a pretty complicated system. There are lots of random perturbations that can affect it ranging from quantum to cosmic rays to chemical and thermal perturbations. All it takes to deactivate a virus is to break one of its many critical chemical bonds so that it can no longer reproduce.

[UPDATE] Wow, five replies posted within two minutes of each other! As other parallel replies have pointed out, oxygen is very likely a significant factor here as it is plentiful and very reactive.

Viruses are nanomachines held together with fairly weak bonds. Rough surfaces interact with and literally pull viruses apart. Very interesting thread here:

https://twitter.com/PalliThordarson/status/12365493051895971...

Just taking a shot in the dark here, but it likely just disintegrates, probably from moisture and even friction from air. That would explain why the "survival" is inverse to the moisture-holding capability of the surface.

Just guessing - molecules of oxygen flying like crazy all around (somewhere read on average 5km/s), eventually at one point knocking something crucial off?

At those scales, these things start to matter.

"SARS-CoV-2 RNA was identified on a variety of surfaces in cabins of both symptomatic and asymptomatic infected passengers up to 17 days after cabins were vacated on the Diamond Princess but before disinfection procedures had been conducted"

https://www.cdc.gov/mmwr/volumes/69/wr/mm6912e3.htm?s_cid=mm...

RNA !== active virus.

"Saying that live virus is there because viral RNA was found is like saying I must be holding a meatball sub because there's a marinara stain on my pants." - https://twitter.com/kenjilopezalt/status/1242285123652825089

Oxygen and the atmosphere.

They disassemble, the atoms find lower energy states.

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