Different diseases, different outcomes.

First, using the total population as a basis is just wrong. Some will certainly be immune to a certain degree while others are simply lucky.

Even very aggressive pandemics, hitting totally ill-prepared societies didn't infect every single person. Not even the black death managed to do so. So why do you think COVID-19 would end up doing that?

And using the 3.4% is another issue. Because you have the Wuhan rate, which is much higher than the rate eslewhere. And this thing is a moving target because testing was rather limted earlier. South Korea seems to be the best source to get mortalitiy rates due to their aggressive testing.

Andrea Ricciardi, Professor of Hygiene and adviser to the Ministry of Health: "The most frightening point is the pitted figures on how much the virus can spread. the curves of the graphs elaborated by the epidemiologists and not only in Italy: according to the models, it could strike until 60% of the population, which means that according to the mortality rates there could be a million deaths only in Italy."

right now in italy it's more like 8% fatality rate

south korea is an outlier and most of their cases are not resolved, they may have a lot of false positives

time to act was weeks ago.