Ask HN: How do viruses transfer across fomite surfaces? | Hacker News Reader

Ask HN: How do viruses transfer across fomite surfaces?

4 pointsExuma2 comments

Lately I've been hyper aware of my own body and how EASY it is to contaminate your house even if you're being extremely cautious.

As a contrived example... you very carefully sterilize a doorknob and your phone, after walking the dog. But you hang the dog leash with your hand which dragged against the ground which touched someone's viral-feces covered shoes. Now you put your hand in your pocket. You realize you touched a dirty dog leash, so you wash your hands again, but it's futile because now your pocket is contaminated.

It's this never-ending game of wack-a-mole.

Now... I dont believe that's actually how a virus transfers from surface to surface.

The current mental model I hold is more like a video game... that if ANY part of the surface touches any other surface, even for 1 millisecond, both are 100% contaminated at a 100% transfer rate.

In reality, I want to understand more HOW (exactly) viruses transfer between surfaces (say, the ground... sand... a piece of cloth like a sock... etc).

Is it more like if you covered your hands in flour, and you touch 2 surfaces, and get 20% of the flour on the first surface, and then 20% of that 20% where on the second surface (an exponential decrease)?

How does it vary between pourous/non-porous or organic/non-organic surfaces?

Does contact time affect it? How about materials.

I found this study but I don't know how to understand it, I don't read medical journals often. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3531458/

Thanks!

It appears to depend a great deal on the all of those factors and more, for example viruses become inactive (unable to infect) over time outside a suitable host environment (depends on the exact kind of virus, surface, and environment.)

There was a recent twitter thread by Palli Thordarson that covers some of the chemistry. The most readable version is: https://www.targetliberty.com/2020/03/everything-you-should-... (HN discussions: [0], [1])

I recommend reading the whole thing, some highlights relevant to your question:

"Most viruses, including the coronavirus, are between 50-200 nanometers – so they are truly nanoparticles. Nanoparticles have complex interactions with surfaces they are on. Same with viruses. Skin, steel, timber, fabric, paint and porcelain are very different surfaces."

"Now it is time to introduce a powerful supramolecular chemistry concept that effectively says: similar molecules appear to interact more strongly with each other than dissimilar ones. Wood, fabric and not to mention skin interact fairly strongly with viruses. Contrast this with steel, porcelain and at least some plastics, e.g. teflon. The surface structure also matter – the flatter the surface the less the virus will “stick” to the surface. Rougher surfaces can actually pull the virus apart."

"So why are surfaces different? The virus is held together by a combination of hydrogen bonds (like those in water) and what we call hydrophilic or “fat-like” interactions. The surface of fibres or wood for instance can form a lot of hydrogen bonds with the virus. In contrast steel, porcelain or teflon do not form a lot of hydrogen bond with the virus. So the virus is not strongly bound to these surfaces. The virus is quite stable on these surface whereas it doesn’t stay active for as long on say fabric or wood."

"The skin is an ideal surface for a virus! It is “organic” and the proteins and fatty acids in the dead cells on the surface interact with the virus through both hydrogen bonds and the “fat-like” hydrophilic interactions. So when you touch say a steel surface with a virus particle on it, it will stick to your skin and hence get transferred onto your hands. But you are not (yet) infected. If you touch your face though, the virus can get transferred from your hands and on to your face."

[0] https://news.ycombinator.com/item?id=22525689

[1] https://hn.algolia.com/?dateRange=pastWeek&page=0&prefix=tru...

Awesome, perfect answer I was looking for. Thanks so much

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