Certain viruses maintained their lethality as time went on. Smallpox was very lethal throughout time. Influenza lethality ebbs throughout history. I don't think we can or should depend on less-lethal, common-cold-like symptoms from Covid-19 at any point.

SARS-CoV-2 does cause common cold like symptoms in the vast majority of cases, just like other coronaviruses. In particular it's quite similar to HCoV-OC43. The only reason those other endemic coronaviruses don't kill many people is that most of us get infected as children and build up some immunity.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7252012/

Is there a reason we shouldn't expect it to behave like most coroanviruses?

There actually is. The evolutionary selection pressure on most coronaviruses exists throughout its infectious stage. So in order to be more infectious for longer the coronavirus would become less symptomatic and so less serious.

But with C19 we are aggressively isolating people with symptoms. This focuses evolutionary selection pressure on the initial infectious stage. In order to be more infectious the virus increases viral load and shedding, causing more serious symptoms; which would be an evolutionary disadvantage, except isolation renders this disadvantage moot.

Also natural immunity general focuses on the nucleus of the virus, vaccine immunity is to the spike. So this forces mutations in different proteins, which has different results.

Are you saying without lockdowns it would have turned in a regular cold by now?

Not lock-downs specifically. Testing and isolating, Maybe, but it would have cost many more lives.

> All viruses get less lethal as time goes on, not stronger,

This isn't true. Given certain assumptions, it's true on average, but those assumptions don't apply in this case.

Agree.

For a specific example the Spanish Flu hit harder later on.

No, it comes from this model:

Highly-deadly diseases will kill their hosts quickly, limiting their spread. Therefore, one of two things will happen:

• A less-deadly variant will emerge, spread faster, and outcompete its more deadly cousin.

• The deadly disease will kill enough of the population that its R number drops below 1, and thus the deadly disease will die out.

Therefore, observed diseases will tend to get less deadly over time.

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If you look at the data, we're firmly in “kill enough of the population” town (to the extent you can stretch this model to our situation). The variants we're seeing spread are getting more virulent over time, not less, because:

• we don't want to die and we're doing stuff about that, meaning any model with “most individuals infected are removed from the model” in it is a flawed model; and

• we have fast long-distance travel, so any population model that relies on Euclidean locality is a flawed model.

I'm not sure I agree with you (yet), but thanks for providing info rather than downvoting!

You haven't cited any data.

> Among the 469 cases in Massachusetts residents, 346 (74%) occurred in persons who were fully vaccinated

> Among five COVID-19 patients who were hospitalized, four were fully vaccinated

https://www.cdc.gov/mmwr/volumes/70/wr/mm7031e2.htm

Here's the thing: even if the virus is less lethal, if it results in more hospitalizations, we are headed for lockdown again if hospital capacity starts getting threatened: all of the routine heart attack, stroke, laceration/crush emergencies we need to deal with routinely will be unable to find adequate care if anti-vaccine holdouts are storming the hospitals for ventilators, or even just inpatient observation. And if our politicians responsibly do lock down to head this off, they probably STILL won't understand how the power was in their own hands to stop it. Businesses will shutter again, kids will miss even more school, and the hospitality industry will again stumble because people refused to understand that even a small number of non lethal hospitalizations spread over the entire population is enough to overwhelm healthcare infrastructure.

> All viruses get less lethal as time goes on, not stronger.

Wrong. It's generally the case, because a virus that keeps its host walking around will tend to infect more people than a virus that sends them straight to the morgue.

SARS-Cov-2 is unusual in that it's asymptomatic infectious period is really quite long. It's straight-to-morgue capabilities could become much more prevalent with hitting its infectivity too badly.

> All viruses get less lethal as time goes on

Smallpox.

Smallpox luckily was a very stable DNA virus with a low mutation rate so it became possible to eradicate it.