Ok, let's look as some more charts to see how the pandemic is progressing. First let's look at Italy.
The top two panels should be pretty easy to understand. These are simply representing cumulative confirmed case and cumulative confirmed deaths. In both cases, we see curves which are nearly exponential growth. But the growth rates are not constant from day to day. To see the day growth factor (the ratio of adjacent day, cum_count(t)/cum_count(t-1)), look at the bottom two panels. Firstly, we can ignore the left-hand side of these sub-plots. Here the counts are too small and the process too underdeveloped to get meaningful ratios. But focus on the trend on the right-hand side. Notice that for the past 3 week these growth factors have been trending down. The can only go as far down as a ratio of 1, since we are dealing with positive cumulative counts. Italy want both of these rates to decline to 1. Once they get to 1 and stay there, the cases have stopped growing. Notice also that death will usually lag a confirmed case and it may take 2 weeks or so for a case to be closed as recovered. So you need to drive down case growth quickly, and eventually death growth rates will decline too as survivors heal up.
We see that Italy is make progress driving down the case growth factor. It's down to about 1.1 (i.e. 10% growth per day), but 3 weeks ago it was over 1.2 (20% growth per day). This is what all their effort as social distancing is accomplishing. It may not seem like much, but it is starting to bend the curve. The death growth factor is also coming down, but more slowly. It's at about 1.15 (15% daily growth). So Italy is slowing this process down, but really they need to shut down transmission much more firmly.
For comparison, let's look at Iran, which is performing comparably to Hubei. (I did not see a recent Hubei chart posted.)
We see that Iran has been much more successful in tamping down case growth. A few days ago it was down to about 1.05, but recently it has bounced back up to 1.1. The death growth factor has also been coming down, but recently it has bumped up just a bit. Maybe Iran has just had some new reporting units come on line, if this is just a data issue. But it could also be that Iran is suffering some renewed outbreak.
Korea gives us a picture of what it looks like to totally shut down transmission.
The decline in case growth over the last 4 weeks is truly impressive. The last 10 days is almost no case growth at all. The death growth factor is still working through the large number of cases that were confirmed weeks ago. This is very effective public health response.
Finally, lets look at the US.
The growth factors here are truly frightening. Instead of declining, the cast growth rate is actually increasing, pushing up to 1.4 (40% daily growth). This high case growth is also driving up the death growth factor, now about 1.3. Case growth is a leading indicator of death growth. So we need to be prepared to see deaths shoot up even faster (on a relative basis) than what we have seen so far. Cumulative deaths will be growing about 40% per day for quite a while. We've got to drive down case growth.
In terms of Tesla returning to auto manufacture, we probably need to see CA (if not the whole US) get growth factors down below 1.05 and keep it there for 2 weeks. Easily this is a 6-week delay.
