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fack_yuo t1_j93qfy2 wrote

as your body fights off the virus the viral load drops, the fever reduces, the body becomes more hospitable for the virus again, the virus is reproducing in cells teh whole time, the cells burst, the viral load shoots up again, the body responds with more fever. I'm sure someone will explain it in more detail but as i understand it thats pretty much it. viral load goes up and down which causes symptoms to be cyclic.


Interesting-Month-56 t1_j93snu0 wrote

To add to this, from the perspective of someone with biology training but not medical…

It is entirely possible that this is an evolutionary response. Fevers kill the disease and, if they go on long enough, the host.

It makes complete sense that a cycling fever provides the most likely survival of the host and that individuals that don’t cycle fevers simply don’t survive.


aphasic t1_j943j0f wrote

It's also worth mentioning that the human immune system is an insane rube goldberg machine where almost every pathway has multiple mechanisms of negative feedback regulation. It's almost universal that when your cells sense a cytokine produced by a viral infection, like interferon gamma, they respond to it (inflammation, fever, antiviral gene transcription, etc), but they also up-regulate genes that serve to dampen the cell's response to interferon. If you put a cell in a steady state amount of cytokine, it will usually have a strong initial response, followed by a damping of the signal. There are a lot of mechanisms by which this happens (down-regulating the receptor, up-regulating the inhibitors of the receptor, etc.)


DorkRockGalactic t1_j94xkxv wrote

Chaos into order, via evolution.

It's like a core metaphor for everything we are and know.


assidreemz t1_j953rl6 wrote

Yea it’s really cool to think about. Entropy is one of my favorite words.


thechilipepper0 t1_j979hne wrote

I tried to explain it to an MFA once. It’s surprisingly difficult to describe in simple terms


Felted_Grape t1_j9egi9o wrote

I like to imagine we are a little backwards swirl going to order in the grand big swirl pattern that overall tends towards entropy.


DorkRockGalactic t1_j9gouep wrote

That's a good analogy really.

With all the random stuff happening, it's possible for things to order themselves by random chance. Earth life happened to order itself just the right way to self replicate and thrive on our island of stability where there are energy gradients to exploit.


SavannahInChicago t1_j96u3o4 wrote

I am currently studying anatomy. Calling the body itself a rube goldberg machine sounds so accurate.


fddfgs t1_j946o2e wrote

Yeah, extended fevers lead to brain damage, which severely inhibits your ability to produce offspring.


Sleepyhowiee t1_j95p0d6 wrote

Given the current state of affairs, I’d argue that brain damage hasn’t seemed to inhibit that much reproduction.


XTJ7 t1_j96lcug wrote

Well, it's not really brain damage for these people but rather indefinite intellectual hibernation. They could use their brains, they just decided not to.


Synkope1 t1_j96mssd wrote

They don't, actually. Fevers have to get up pretty high, to 107-108 to cause brain damage, which is pretty darn rare. I can count on one hand the number of fevers I have seen over 107.


kharmatika t1_j9593fn wrote

Lol I love this for some reason. “We done being on fire yet?” viral load shoots back up “nope.”


honestdiary t1_j94wzdv wrote

I believe so. Too high of a fever, or too long of a fever, your organs start to cook.


MrDilbert t1_j96iviq wrote

Side note: that's actually the reason why Ebola is so dangerous: its natural reservoir are bats who have higher body temperature than humans, so when the human body wants to get rid of it, it has to ramp up the fever. And since the virus can handle higher temperatures, the fever has to run hotter and/or longer to kill it off, but has a very high chance of cooking the internal organs as well.


JustAnotherMiqote t1_j9444mw wrote

Having a fever that lasts longer but doesn't kill you seems like a pretty good evolutionary trait tbh..


diamondpredator t1_j94sz06 wrote

I thought it wasn't the fever that killed the virus but that the fever made your own immune cells better at defending against it because the higher temperature is a better environment for them.


JohnnyJordaan t1_j95ej4n wrote

It doesn't outright kill individual pathogens, but it does combine the effects of making it harder for them to survive (so letting the population die out) and increased production and activation of immune cells. But that doesn't mean it's a better environment for them than normal body temperature, as of course the system is designed to handle 99% of the infections in that condition. Fever really is the fallback scenario where all bets are off until they fix the issue, causing all the other effects we call 'being sick'.


ClownsAteMyBaby t1_j956p6p wrote

Not that I've ever read. It's generally taught that it makes the environent less hospitable to viral/bacterial enzyme function and replication.


laughingweasel t1_j9661vh wrote

And it really slows down the rate that viruses multiply which allows your immune system to reduce the number of viruses that are able to multiply.


bonkly68 t1_j991tac wrote

I've heard that white blood cells are about twice as mobile per degree C of temperature rise.


No_Habit4608 t1_j95gfal wrote

So, based on this, does taking a fever reducer (e.g. acetaminophen or ibuprofen) also reduce the fever, and/or the body’s ability to fight the virus?


nurseliz21 t1_j95iheg wrote

To a certain extent, yes. You should take an antipyretic if your fever is high (above 39.8°C) and doesn't break. At least these are the recommendations I've always gone by myself. It just prolongs how long the body will fight off the virus. This is the same for cold and flu medicines.


zhibr t1_j96dfv3 wrote

Right. If the fever would be at its height for the whole time, there would need to be a specific mechanism that stopped it when its not needed anymore. That's much more costly, in evolutionary sense. With a cyclical one, each fever is supposed to die on its own, so it's just a matter of trying again if the previous one didn't work.


Gamebird8 t1_j96oby3 wrote

And fevers are often just an attempt to mitigate until you can produce an adequate antibody response


theaussiewhisperer t1_j954c5g wrote

You guys are so bloody smart. I thank you for your time sacrifices for the betterment of our society. Scientists honestly deserve glory only reserved for humanitarians and warriors.


[deleted] t1_j93sui0 wrote



fack_yuo t1_j93t4bk wrote

lol. well arguably, if the fever does not injure you then it will clear the virus faster yes. Unfortunately evolution is a case of what does not prevent reproduction as opposed to what is most optimal. Fever kills virus, but it also can injure the host. General rule - don't reduce fever unless the fever is dangerous. (if clearing the virus is the top priority- generally survival is top prioirty and its preferable to manage the fever and prolong the illness slightly. ) - disclaimer, not medical advice.


wewbull t1_j95tpui wrote

Sounds like a classical control feedback loop in engineering.

However if it was just this there'd be no reason the body wouldn't have developed some kind of hysteresis to "debounce" the system, latching the fever on for a period after the viral load drops to ensure the complete eradication of the virus.

I suspect the fever is expensive or damaging in itself. So the best system is something less drastic, but that might take longer to kill the virus.


Shadowfalx t1_j96254v wrote

There also isn't a reason to think the body would evolve a way to stay in fever after vital load drops. Remember, evolution is random and if this never randomly occurred we wouldn't evolve it.


wewbull t1_j964efw wrote

It's random in the short term. In the long term, beneficial traits will improve survivability and be selected for. If staying in fever benefitted surviving it's reasonable to assume it would have arisen by chance and then been selected for by now.


yaminokaabii t1_j96bbp2 wrote

Be careful saying that beneficial traits will necessarily become more prevalent. It's all probability. If getting the long-term better trait necessitates going through a worse trait in the short-term, it may never happen. As an example with arbitrary numbers, say staying in fever another 1 to 5 hours is actually disadvantageous, even if staying 5-10 hours is advantageous.


wewbull t1_j96d4tw wrote

True. Local inflections like that can act as barriers to getting to a much more advantageous trait. I agree.

...but I also think it's wrong to say evolution is random. It's random experiments in a game of procreation. Those experiments which fail are discarded. As such the overall process is guided away from failure and not random.

Maybe I was asserting the positive case (towards success) too much, when the negative case (away from failure) is really the stronger aspect.


yaminokaabii t1_j96lbr8 wrote

I had just wanted to add to your last comment, I think we are in violent agreement here! Saying evolution is "random" is simplified to the point of inaccuracy—I would say it is probabilistic.

There is definitely something to be said about going towards success. I'm thinking of the RNA world hypothesis about the origin of life wherein RNA molecules both held replicable genetic information (as DNA does) and catalyzed the chemical reactions to replicate itself. The self-sustaining molecules won out because... they sustained themselves. Life now is pretty damn good at "being successful", except when it's threatened by other life being more successful, which looks like moving away from failure.


Shadowfalx t1_j9756f9 wrote

You are correct but are missing the forest for the trees as they say.

The original mutation is random, benefiting (or at least not harming) is selected for. So without the random mutation there isn't anything being selected for.

For example, say we need to change gene 1 from A to C for the fever to last 1 hour longer (this is very simplified of course) but throughout history no one has changed gene 1 to C then there will be no longer fever to select for.

We can't see evolution as something that moves creatures along with intent. Nothing is guaranteed since you must first have a random mutation to progress.


kuh-tea-uh t1_j94msj7 wrote

How long does a fever cycle typically last? Are we talking like every 15 minutes, or every few hours?


Patak4 t1_j94pcru wrote

Defintely every few hours for a cycle. Tylenol will dampen the ups and downs


th3h4ck3r t1_j96c6u3 wrote

That just sounds like a second-degree differential equations with extra steps.


[deleted] t1_j94aqbi wrote



light24bulbs t1_j94yae8 wrote, it's probably not a caloric constraint. Being hot is pretty damaging to the host as well.

Maybe you should source the calory thing?


Mercerskye t1_j956q5z wrote

Starving to death is arguably more damaging than a fever, with the odd occurrence of infections that prompt a fever high enough to be lethal.

Closest link I can find talking about calorie restriction vs inflammatory responses.

It makes a lot of sense though. We practically have nothing left to adapt to, at least not on a major level. Our last big changes were at a point where food wasn't a daily guarantee, but getting some kind of injury or infection was pretty likely.

Our ancestors that could fight off an infection long enough to get to the next meal, or at least survive long enough to reproduce are, imho, the better candidates for passing genes compared to those that just kept trying to "burn the infection out."

1000yrs ago, just hanging around spending all your fuel for what amounts to no forward momentum in the survival game was probably a fast ticket out of the gene pool.


Shadowfalx t1_j961xa3 wrote

This is the worst kind of amateur take.

Humans have generally had a few days to weeks of fat reserve plus some extra weeks with muscle. The calorie cost of raising your temp 4°F is low. Plus, we have, since becoming human and probably long before, lived in groups (often familial) that help each other.