> they said the normal influenza's fatality rate is 0.1% ~ 0.2%
Even if you stick to just the cold numbers, the math is based on some wrong assumptions.
The quoted 0.1-0.2% rate is an effective rate which accounts for all the mitigating factors in place to fight the flu. Things like medication, hospital care, even the flu vaccine which is generally believed to lower the impact of the flu in cases where it did not prevent it outright.
Absent those mitigating factors, the death rate would be significantly higher. Country level statistics show differences in flu mortality wider than tenfold, correlated with (among other things) the quality of their health care system.
However, the existing systems are "tuned" to the characteristics and scale of the known flu. Throw at those systems a pandemic that can bring 100 times more cases at once, and they will simply not have the capacity to handle the 99% excess cases. Those will be left to let the disease run its "natural" course at the higher "unmitigated" fatality rate.
Even with the common flu, if all the cold season infections happened during the same week, the death rate would be well higher.
> and the death rate due to coronavirus is about 0.2% ~ 0.4%
This alone makes the above several times worse. On top of that, the contagion rate is higher for covid-19 than the flu, at least twice higher, and the effect on the spread is exponential. That pretty much guarantees a quick and high "peak" of general population infection if left unchecked.
Add to that all the other unknowns still in the picture - no standard/established treatment, no vaccine, not even a consensus on whether the infection confers future immunity or not etc.
Bottom line, I don't find it surprising in the least that (most) people and governments would take the threat seriously.
Liviu