Take deaths, multiply by 400 and that's how many cases you have. This comes from the assumption of 1% mortality and 3 weeks to die. I don't see where 400 comes

Take deaths, multiply by 400 and that's how many cases you have. This comes from the assumption of 1% mortality and 3 weeks to die. I don't see where 400 comes from. If we assume that people who died today now are 1% of those who got it 20 days ago, then that is a factor of 100. Project that forward through 4 doublings for the fact that we have about 20 days of doubling every 5 days and we get to a factor of 1600. You can complicate the toy model in a number of ways, but I can't get it as low as 400. Anyways it is worth pointing out that the curve of reported cases will continue rising for a couple of weeks as people both get symptoms then get sick enough to come to the attention of hospitals. And if the measures work, it won't be obvious from death rates for about 4 weeks. And at that point the critical question is whether we managed to slow the rise, or create an exponential decline. My bet is that we are only going to get a slow in the rise. Hopefully enough for us to get ahead of the need for emergency treatments.