Earlier quoted context omitted.
3% of the infected, not 3% of everyone. You can't compare it to WW2 unless you assume everyone will be infected.
If you don't control a disease, the default assumption is that it infects a substantial fraction of the whole human population. In almost all examples in human history, whenever a disease stopped, it was either because it burned through most of humanity, or because people decided to make it stop. They don't stop themselves.
You're pretending we live in the 1400s. We don't.
You're pretending we will take no measures to control this at all. That's simply not the case.