COVID-19 From an Evolutionary biology standpoint

COVID-19 From an Evolutionary biology standpoint:
Just want to preface this by pointing out that I am not an epidemiologist. I have however spent quite a bit of time researching credible leaks, and peer-reviewed papers. I could be wrong about all of this, but biology is...simply put, biology.
Below are my musings from an evolutionary Biology perspective:
From a straightforward biological/evolutionary perspective, virtually every single vertebrate population of every species will experience various viruses and bacterial infections throughout their evolutionary history that will cause massive die offs, everyone now and then.
This is normal, this is part of evolution, and has been taking place on this planet for hundreds and hundreds of millions of years, since the evolution of vertebrates. We can go further back, to the beginning of the evolution of multi cellular life - but for the sake of simplicity, we'll stick to vertebrates.
Vertebrate Populations cannot grow exponentially, at some point, either resources run out, there's a stochastic weather event, or a super volcano, etc that limits population. Or, in some cases, population density increases beyond a threshold where communicable diseases spread like crazy, and wipe out a certain % of the population. This is normal, natural, and common in evolutionary history. Avian flu is a good example: Happens normally, naturally and can totally wipe out entire populations of certain migrating birds.
In some species, this leads to extinction, in others, it just simply dramatically drops their populations back leaving the ones with resistant genetics to carry on. Other (majority of) instances simply lead to a die off- followed by re-growth with resistant genetics.
Let's talk about the human species. COVID-19 is fairly typical of viruses that once were common in society. Measles, mumps, rubella, smallpox,, etc., all had R0 values 4 to above7.0, and would go through the human population (i.e., civilization) and cause massive outbreaks, followed by survivor genes spread to subsequent generations.
Below are a list of common viruses/bacterial infections that were once extremely common in society:
R0 Values of common Human viruses that were once extremely common in society (but were NOT novel):
Measles Airborne 12–18
Diphtheria Saliva 6–7
Smallpox Airborne droplet 5–7
Polio Fecal–oral route 5–7
Rubella Airborne droplet 5–7
Mumps Airborne droplet 4–7
Recent work at Los Alamos National Laboratory, Kyoto University, and University of Georgia indicate an R0 value of COVID-19 between 4.7 and 7.0 (this is an AVERAGE R0 value without any quarantines in effect). These same studies indicate that with quarantine, R0 value is still 3.0 or higher.
OK, so back to my Musings: For 99.9999% of human history, viral outbreaks and bacterial outbreaks were a leading cause of death. It's just in the last 100 years or so that such causes of death were averted for a variety of reasons.
Well, COVID-19 is a novel virus, meaning that there's little "built in" immunity. I'd be a crappy Biologist if I didn't acknowledge that there are some mild coronaviruses, which might explain why the critial illness rate is 20%+, rather than 80-100% - so, it's worth "thanking" all those common colds - they likely have helped contribute to some innate immunity. However, the severity of COVID-19 is orders of magnitude worse than the common cold - which is our only evolutionary exposure to coronaviruses of this nature. Perhaps the term "novel" coronavirus is somewhat misleading - it's not a totally novel brand of viruses, but this one is quite a bit different than the common cold, genetically speaking.
For better or for worse, humans are now, subject to the same "rules" as every other species - they get to experience natural selection for the first time in quite a while.
Why COVID-19 is possibly permanent:
Reports indicate that 80%+ of those exposed to COVID-19 will get infected. With an R0 value of 4.7-7.0 it's guaranteed this virus will spread to nearly every human on Earth. The 14-28 day asymptomatic period guarantees the spread, and makes it literally impossible to detect and stop outside of 100% lock-down quarantines. Even such quarantines are ineffective. Why? As soon as the quarantine is over, the virus will just start over again - it's not possible to eradicate COVID-19 - it's permanent. It'd be like trying to permanently eradicate the common cold. It's NOT POSSIBLE for a variety of reasons?
Immunity only lasts for up to 6 months - after that, re-infection is 100% possible.
R0 value extremely high - even a single person in a crowded factory, or subway will easily re-ignite Wuhan all over again - with a 6 month immunity, that means that even after quarantine, everyone who got that virus 6 months ago will get it again...and again. I'm 33 years old, I get the common cold every single year - that's a coronavirus. Coronaviruses have conservative evolutionary features, just like Flu viruses, etc etec.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4125530/
" Follow up studies from patients who recovered from SARS suggest that the SARS-CoV-specific antibody response is short lived. In these patients, SARS-CoV-specific IgM and IgA response lasted less than 6 months, while virus-specific IgG titer peaked four-months post infection and markedly declined after one year. "
That being said, It's worth mentioning that SARS and MERS did fizzle out, and sort of "disappeared." Throughout human history, viruses would also sort of just "fizzle out" - inexplicably. Many religions proposed "reasons" for why viruses just "disappeared" one year after a massive outbreak. The 1918 Spanish flu was the same way. Not before they wrecked absolute havoc on civilization, but yes, in many instances highly contagious and deadly viruses "miraculously" disappeared throughout history.
What about survivors?
In this current situation with COVID-19, survivors will be all over the planet - highly probable that many individuals simply cannot catch COVID-19, or have extremely mild symptoms due to genetic variance. This is basic evolutionary biology. Even Smallpox with the native americans "only" killed off 50% of the population, the other 50%? They were resistant and had natural immunity to the virus.
Again however, this is simply nothing new. Smallpox, Measles, Boubonic plague, Yellow Fever, etc used to spread like crazy all over the world in previous decades. What was the difference? Well, back then there were only 750 million humans spread all over the planet. Similar to half the population of China.
In fact, there's more humans in China right now than existed for 99.999999% of human history. From a biological standpoint, a virus outbreak was inevitable with such population density.
When was the Last time Something Like COVID-19 Happened (Smallpox to Native Americans)?
The last time, from a human standpoint that we've ever faced a virus with 80% infectious rate, and an R0 value of 4.7 - 7.0 was Smallpox on the Native American population. Smallpox has an incubation period frighteningly similar to COVID-19 (up to 14 days!).
Smallpox had an R0 of 5-7 - which is nearly identical COVID-19. Smallpox (in a NOVEL environment) had a death rate of 25-50% (in certain populations, nearly 100%). Interestingly, smallpox also had a 14 day incubation period.
COVID-19's death rate is considerably lower, but without hospitalization it's not unlikely to have a 20% mortality rate. In fact, leaks from China indicate that nearly 50% death rates are being recorded. If true, this will quite literally, be apocalyptic. Similar to the events that the native American population faced with the Smallpox Virus when Europeans first introduced it.
Historically, reports indicate that Europeans would enter former Native American cities only to find a handful of survivors - many tribes ended up banding together, and consolidating - it's estimated that 20+ million Native Americans died from novel viruses. In short: Novel viruses are actually quite rare. The only TRULY novel virus to human populations was Native Americans. The 1918 spanish flu, while novel, was still a flu. In that sense, COVID-19 is actually a bit like the 1918 Spanish flu: the common cold is a coronavirus - so there's a mild amount of innate immunity.
In short. If we'd like to peer into the future, it's worth researching the smallpox Mumps, rubella etc. outbreak among native Americans. This is quite honestly the ONLY good example that we can go by right now - as there have simply not been particularly many novel viruses, outside of the 1918 Spanish Flu with high R0 values and the ability to survive on inanimate objects for so dang long (and long incubation periods).
What about the 1918 Spanish Flu?
Let's talk about that comparison. The problem with comparing COVID-19 to the 1918 Spanish Flu is that the R0 of the 1918 Flu was substantially lower, and the incubation period was substantially lower. Comparing COVID-19 to the Spanish Flu of 1918 is not accurate, as these are vastly different viruses.
The fact that COVID-19 has a remarkably high chance of re-infection, with a long asymptomatic period, and lengthy survival time on inanimate objects, makes it rather dissimilar to the 1918 Spanish Flu.
What are the similarities? Well for one, both COVID-19 and the 1918 Spanish Flu can lead to rapid death, and entire families can die. In fact, the Spanish flu was notorious for occasionally killing in a remarkably short period of time. We're currently seeing numerous people dropping on the streets of South Korea and Iran. There was a report of a Chinese Film director who lost his entire family - that too happened in 1918. Both the 1918 Spanish Flu and COVID-19 attacked the lungs, and had a cytokine storm. Check and Check, unfortunately. That last part, the Cytokine storm is particularly dangerous - and was the same reason that the 1918 Spanish Flu could kill so rapidly, even young, healthy individuals.
Another key difference is that COVID-19 tends to affect different demographics - 1918 Spanish flu mostly attacked youthful individuals, while COVID-19 tends to affect more elderly individuals. That's not the reason it's a bad comparison however. THE REASON it's a bad comparison is that the R0 of COVID-19 is much much much higher, lasts much longer on surfaces, much longer incubation period.
One could say this is a much more severe "version" of the 1918 Spanish Flu - but to compare it directly wouldn't necessarily be accurate - COVID-19 is a totally different beast.
In conclusion, novel viruses are normal, and part of evolution. The 1918 Spanish Flu is a bad example to compare COVID-19 to, because the R0 value of COVID-19 is substantially higher, and the asymptomatic period is substantially longer. On the other hand, Smallpox of the 1400s-1800s would be a much better example, as R0 value of 7.0 is quite similar to COVID-19 - and the ability to live on surfaces for weeks, droplet spread, etc., is also quite similar.
I am a biologist, but not an epidemiologist. These are my musings, stay safe out there.
TLDR: The 1918 Spanish Flu is not a good comparison to COVID-19 because the R0 value was much lower, and the asymptomatic period was much shorter. Smallpox to the native Americans is a far better comparison because the parameters of COVID-19 and smallpox are quite similar (including a 14 day incubation period, droplet spread, and R0 value nearly identical to COVID-19).
References:
Basic Reproductive Number: https://en.wikipedia.org/wiki/Basic_reproduction_number
Smallpox Native Americans: https://www.historynet.com/smallpox-in-the-blankets.htm
R0 Value of 4.7-7.0:
Los Alamos National Laboratory: https://www.medrxiv.org/content/10.1101/2020.02.07.20021154v1.full.pdf
University of Georgia, Kyoto University: https://www.medrxiv.org/content/10.1101/2020.02.12.20022434v1.full.pdf
Smallpox info: https://www.mayoclinic.org/diseases-conditions/smallpox/symptoms-causes/syc-20353027?page=0&citems=10