This was the pattern with SARS which is closely related to COVID-19. That disease was quickly driven into extinction because even in its milder forms it was so dangerous that people took it very seriously.
COVID-19 has resulted in many more deaths in large part because it was more mild. People and governments were reluctant to take the actions necessary to control it.
The Chinese noticed early on that there were two strains of COVID-19 one much more severe than the other. Both strains were also found outside China. Chinese researchers said that the milder strain, which in early January had been a tiny portion of all cases, was rapidly becoming the dominate form.
Is this happening in the rest of the world? I have heard little about this in recent weeks.
Nevertheless, this is another reason to use masks and social distancing to slow the spread of COVID-19. Over time, and it actually a rather quick process, COVID-19 is likely to become much more mild.
Slowing the spread has many other advantages. It gives us a chance for testing to get ahead of the spread and stop it as it has done in South Korea. They have at this writing only lost about 250 people, in spite of the fact that they were the worst hit outside of China early in the epidemic.
Slowing the spread also gives us a chance to deal with shortages of equipment, like masks and ventilators, prevents the medical system from being overwhelmed, gives us time to find treatments, and even ways to prevent the spread and much more.
So stay safe. You can not give what you do not have. If by being careful you avoid COVID-19, you protect yourself, your family, and society.