Recent history doesn’t do much to support the idea that diseases from animals always become mild as they adapt to spreading in humans. Consider HIV. It spreads before you get sick, so it’s no problem for the virus that after a few years, without the right drugs, 100 percent of infected people die. As we have seen, it hit humanity in the early 20th century, it eventually went very much pandemic, and it’s shown no sign of getting nicer in all that time.
