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Comment by phreenet | Hacker News Reader

I'm no expert on this and this isn't a political post although it's been politicized, please don't beat me up.

Can someone who is knowledgeable explain to me how this virus could have evolved in nature with such sensitivity to UV light? I've heard it explained that the driving belief that this virus was modified in a lab for study of SARS class viruses and escaped (not released, not as a weapon) is because it never had to adapt to sunlight. Is there a way that science could answer or prove this virus is in fact a natural mutation/evolution?

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Almost all microorganisms as suspectible to UV light. The damage happens at the DNA level (UV light causes a thymine dimer when two thymine nuclobases are found together in DNA... thymine being the T in the AGCT of DNA code). This dimer can result in frameshift mutations which can result in a bunch of different damage depending on where the TT bases are (some mutations result in no change, some result in cells inability to replicate etc).

So that's the background on how the UV light acts and disrupts a cells ability to survive. Now, about your question on how could a virus evolve if UV light kills it. Easy... the virus doesn't spend a ton of time outside of your body. Most transmission is person-to-person, there isn't a ton of person-to-surface-to-person spread therefore it's not like the virus is sitting on a handrail in the sun for days. Also, as I mentioned above, some mutations don't result in any change. There is a lot of redundancy in the DNA code (see DNA codon table 1). Not every combination produces a unique aminoacid.

1 - https://en.wikipedia.org/wiki/DNA_codon_table

My microbiology background is a bit dated, so my facts might be a bit off here and there.

Also it's really important to conceptualize the sheer scale at which a virus operates. One single virus isn't a problem, but when it enters the host's body and replicates, you're talking about millions of the little things. Some of them will die off to all sorts of natural causes and that's (from the virus's point of view) not a problem so long as enough of them survive to continue replicating, in their host, in some adjacent host, etc.

I guess this is the science behind the statement "sunlight is the best disinfectant" through the ages.

Correct. Since UV light acts at the molecular level and at the very core of what makes the cell work (DNA or RNA) it's hard for organisms to overcome. There are mechanisms of fixing these dimers, but cells need to produce them (which uses resources). Therefore there is a trade off, create too many fixes and something else has to give, create too little and a little UV light kills you.

> Most transmission is person-to-person, there isn't a ton of person-to-surface-to-person spread

So I've heard. Doesn't this mean that the UV news is of little impact?

Yes, somewhat. I was involved in a project a few years ago where we installed specialized light housing in the ceiling at the hospital I worked at. These units had a UV system above it. Basically it would circulate air over UV lights and therefore would help to decrease the amount of virus floating in a room. So potentially this could help with a system like that but that only solves a small portion of person-to-person transmission. Much of it still happens with-in family groups where you are sitting and talking/hugging/kissing etc. That's why mask wearing and physical distancing are key.

Plus it's a bat virus originally, and bats are largely nocturnal, and also roost in dark areas like caves during the day. Resistance to UV light is not that useful to a bat pathogen.

Sunlight doesn't contain any 222 nm light. That's why there's no selection pressure for a virus to be able to survive irradiation at 222 nm.

This is the probably the right answer. See e.g., this link https://commons.wikimedia.org/wiki/File:Solar_spectrum_en.sv... for what wavelengths of sunlight reach the earth’s surface.

You could ask how humans evolved in a world that is mostly water and humans drown so easily. They are also present in regions surrounded by water? How did they get there?

They developed in places that are not water and moved to other places through water by occupying small spots of non-water while in transit.

Same with the virus. It developed in places that UV doesn't reach, like insides of larger living things, and travel to other habitable places by exposing themselves to UV only very briefly while being somewhat shielded by water in breathed out droplets.

You just described bats that live in caves, like vampires and only come out at night.

>with such sensitivity to UV light

I don't think the sensitivity is specific to COVID-19. I believe it extends to all coronaviruses, if not all flu viruses.

Use of UV lamps as a germicidal goes back to the 1930's, so killing organisms with UV isn't new. Either the intensity, duration, or wavelength of the light could be different from sunlight.

It hypothesized that cellular life evolved in deep, dark, warm places in the ocean. Geoboiologist Robert Hazen experimentally found that most stages of basic metabolic citric cycle and RNA reactions do not require enzyme catalysts to proceed there. Then as life expanded to cold, low pressure bright sunlight areas they developed enzymes to assist metabolism and protein synthesis there.

Most viruses dont contain the mechanisms to resist damaging solar radiation

all viruses are susceptible to UV light. Ultimately it spread in bats so it is pretty obviously able to spread in caves. It also spread in people indoors.

There is virtually no way for scientists to look at DNA and say "oh yeah this was manmade" (or not manmade). Possibly if there is some really obvious splicing marker used or something.

the entire sequence can be put into a computer and custom generated.

There are, however, strong indications. I don't have my cites handy, but IIRC for COVID, they were twofold. One, it relied on a mechanism that pre-COVID was considered ineffective/borderline for spread, and that actually doesn't work well in simulations - so it's unlikely humans would've picked that. Two, it's closer to typical bat viruses than typical coronaviruses - again, an unlikely choice for humans to make.

Ah, here we go: https://www.livescience.com/coronavirus-not-human-made-in-la...

No, that doesn't rule out manmade 100%, but it makes it quite unlikely. It's essentially saying "hey, I built a virus in a structure that doesn't rely match a well-working virus class. Also, it completely fails to do what we want to do in simulations. We should invest a lot of money to build that".

Occam's barbershop would like to point out the very high number of unlikely events required to go down that path ;)

I would say it's a case of large surface area to volume ratio, inability to repair damage, and lack of selective pressure (why protect yourself from sunlight when you spend your time inside an animal?).

No great mystery.

We know it wasn't lab made. We've know this since March.

https://www.nature.com/articles/s41591-020-0820-9 https://www.sciencealert.com/here-s-what-scientists-think-of...

Absence of evidence is not evidence of absence. Now, realistically, it probably was not made in a lab. But it is not true that we know that.

There's plenty of evidence it is not lab made.

There's some evidence that is suggestive, but far from what anyone knowledgeable would consider proof.

> but far from what anyone knowledgeable would consider proof.

Which is why the comment said "evidence" and not "proof".

Read the Nature paper.

If you are going to be pedantic, there is no such thing as 'proof' at all. You can only ever demonstrate that you are 9X% likely to be correct.

Maybe the murder caught on camera is a lost identical twin, or victim of a very elaborate frame-up. The standard for conviction is beyong reasonable doubt. What is reasonable?

Maybe we have laws of physics wrong, and next tuesday sun will rise in the west, and Jesus rises from the dead. Again.

Do yoy trust governments and scientists? They used to claik smoking is a great way to get your essential vitamins.

Do you trust your own mind, because research has shown people can be manipulated into remembering things that never happened.

Ib radical doubt, the only thing you can proove is 'I think, therefore I am".

So then just give voice to unsubstantiated rumors that contraindicate what we see in the genetic marker?

Also I'd like to contest that the nature study is "suggestive" that its not man made. Finding Elvis dead in Vegas is not "suggestive" that Elvis is dead.

If you are asking me to proof a negative, that's virtually impossible.

That's a kind of dangerous line of thinking.

It's impossible to prove that it was not grown in a lab, which is why the burden is to show that it _was_ grown in a lab. Until we have that, we shouldn't be sharing stories about how it _might_ have been grown in a lab.

I don't think it's "dangerous" to acknowledge that it is possible the Coronavirus was grown in a lab.

It is extremely unlikely that the virus was grown in a lab, because it's unlikely anyone has the technology to create a virus quite like this one.

The last decade has given us some pretty good illustrations of how it can be dangerous to give credence to baseless conspiracy theories.

Logically and epistemically sound thinking is what the world needs more of, not less.

I presume you're not a big fan of conspiracy theories - well, a big part of where they come from is the media doing something similar to what you're complaining about, stating what might be true, as unequivocally true. It would also be interesting to know how much of the polarization in society can be attributed to the fantasy world the media projects into people's minds using these techniques.

I’ll share whatever stories I please.

The probabilistic model of knowledge as just a collection of hypotheses that have failed to have been falsified over sufficient testing is the dominant epistemological view today in empirical sciences. Knowing = Probably Is. It's just a matter of degree, so making the statement "it is not true that we know that, but it probably is the case" is ill-formed in the absence of consistent belief thresholds.

Normally I wouldn't say anything, but you did pull a "well, actually" there, so out-pedantifying seems warranted if only for the humour of the situation.

The downvotes on this are interesting - this is not a settled matter?

I think there is a very big misunderstanding with this. Now, I'm not an expert, like most people commenting on this, but this is my understanding from listening to other experts.

Scientists pretty much agree that this virus was not created in a lab. Howver, that doesn't mean the virus could not have been taken into a lab from the wild and allowed to reproduce under controlled conditions and basically speeding up the evolutionary process to make it more virulent in order to make it easier to study in lab conditions.

This is common practice in lab study and is not possible to tell definitively that it has been done. Because it doesn't involve genetic manipulation per se. It is simply an artificially manipulated environment for the virus to grow in "naturally".

It has been suggested that the propensity of the virus to spread well indoors rather than outside may be due to the fact that it spent time indoors in a lab selecting for that before it escaped back into the wild.

If it spread among bats, I could see sunlight not being a selective pressure on the virus. They're nocturnal animals, right?

How could the virus have spread worldwide with this sensitivity to sunlight?

How could we have evolved from single celled organisms?

Airplanes

Indoors?

My understanding is that this coronavirus originally evolved to infect bats. Presumably, bat to bat transmission would be mostly at night, so not much evolutionary pressure for the virus to last long in sunlight.

I thought the bat thing ended up being untrue?

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