No reason to be afraid of new strains. Coronaviruses become less deadly as they evolve to become better at spreading.
Pre-symptomatic infectiousness has about the same selection pressure as low mortality rate IMO. Low risk viruses circulate well because people don’t care about transmission very much. High risk infections cause people to take precaution and thus eliminates those stains. SARS-COV-1 and MERS were that way.
But pre-symptomatic infectiousness (SARS-COV-2) makes this calculus immaterial for most people; they transmit it without knowledge. This reduces the pressure on high mortality / morbidity strains / variants.
LONG TERM, less deadly viruses will tend to spread better because the more deadly a virus is, the more it raises stakes for the host population to remove it or prevent it , and the more it can make it apparent who has been infected. Ebola for instance justifies pretty almost any action you can imagine to contain it's spread, where we are still arguing if lockdowns or travel restrictions are the cost appropriate measure with COVID.
If the time of fatality is sufficiently delayed, or the time to implement other countermeasures or recognize the situation has changed is too long, it doesn't help anyone in the short, medium, or potentially even long term - you can have massive fatalities and huge spread.
The 1918 pandemic had multiple waves, with the second in particular having a much higher fatality rate than the first - 10x a typical flu season, which is what we're seeing now. This was almost certainly caused by variants, though lack of data makes it impossible to prove. [https://en.wikipedia.org/wiki/Spanish_flu]
A particularly nasty example [https://www.adn.com/alaska-news/science/2020/03/22/how-an-al...]
The more infections, the more likely we'll get more variants, and the more likely we'll get some that cause terrible, terrible problems - and may still be quite infectious.
Long term, will the most terrible ones die out? Very likely. However, smallpox was a scourage on humanity since likely 300 BCE and up until eradication by a massive global effort in 1975, it still had fatality rates around 25-35%. So don't just assume COVID will 'evolve to harmlessness', or if it does that it would happen on a timeframe convenient for society [https://www.cdc.gov/smallpox/history/history.html]
Soldiers with minor symptoms remained where they were, not coming in contact with many other people.
The very sickest soldiers were transported by train, where the infected many other people, to hospitals, where they continued infecting many other people. It was our own attempts to care for the soldiers that caused the deadliest strains to spread and continue evolving.
What some folks are proposing in this thread (uncontrolled community spread so it will 'mellow out') is an even more massive expansion of that due to the quite visible ability for COVID to be infectious in patients with no symptoms for long periods of time, which Influenza has not been able to pull off.
So we have no reason to believe this will occur with covid19.
Not necessarily. Assume that people try to self-quarantine as soon as they notice symptoms. (They don't need to be 100% effective at this.) Consider "mutations that affect how quickly it spreads within your body". Those that increase said efficiency would presumably increase the likelihood of death; but they would also probably shorten the "asymptomatic spreading" period, which means they'd get selected against; this selection happens even among those that aren't dying.
(Author background disclaimer: No biology beyond 9th grade.)
The common cold is a coronavirus. It is significantly less deadly than the seasonal flu. We have every reason to believe that a more contagious but less deadly version will resemble the common cold.
.3% of New York City has already died.
Unless the vast majority of New Yorkers have already contracted the virus, the mortality rate has to be substantially higher than .3%.
SARS-CoV-2 is also only ~3x as deadly as the flu WITH UNPRECEDENTED MEASURES TO CONTAIN IT. In areas where it wasn't contain, such as the initial outbreak in Italy that overwhelmed hospitals, it was 10x or more as deadly as the flu.