Don't look at the lit fuse. Look at the bomb it leads to.
NYC death numbers double in under 2 days now.
Using CDC's FluView app I looked at the 2017/2018 flu season to see what the doubling time was. It's not 3 days indeed. It varied quite significantly during the outbreak, but there were periods where it was doubling approximately every week. Potentially faster I suppose depending on how closely people were looking for it (not that close if I understand correctly for most flus).
Viruses can grow pretty fast.
The problem is, as bad as the current numbers are, without significant changes, they are inevitably going to get considerably worse quickly, as you can see from the graphs.
Imagine what'll happen if 60% of the US population gets this quickly (over the next 3 months say) and then 2% of those people die with another 8% in hospital...
But with covid-19 the numbers of people dying is doubling every 3 days.
80, 160, 320, 640, 1280, 2560, 5120, 10,240, 20,480
Potentially Covid-19 would hit that 29200 figure in about 25 days from today.
https://www.ft.com/coronavirus-latest
https://www.worldometers.info/coronavirus/country/spain/
8th 17 deaths
11th 55
14th 196
17th 533
20th 1093
23rd 2311
26th 4365
Imagine 81 people died in a bus accident, or a fire, or a mass shooting. This is very serious and we're still at the beginning of it.