If you want to understand what my assumptions are and what my methodology is, it is described in this post
It’s the end of day 1 and eNCA reported that we now have 1170 infected cases of COVID-19. It is weird how an increase from the 927 of the day before can be good news and yet it is.
Why is this good news?
A quick reminder about day zero. it is the day that the ceiling of infections is reached. In today’s post that is set at 65% based on some harsh criticism from the internet. I stress that I am not saying that 65% (or 100%) will be infected, only how long it will take to infect that many people.
The good news is that because of the slow down, day zero has shifted from 7 May to 11 May. I know that is only 4 days but look at the chart above. It means that by 7 May only 15 million South Africans are infected and not 36.8 million (65%).
Big deal? Yes, it show how dramatic the slowing down can be on the final outcome.
I explained in my first COVID-19 post that even when a race car is still accelerating there is a point at which the acceleration slows down. At first, this is a difficult concept to grasp so let me try and explain.
If a sports car currently travels 10 m per second and accelerates at a 2 meter per second (per second for the engineers). One second later it will be doing 12 m per second. If it continues to accelerate the acceleration to add 1 meter per second every second, it will be accelerating at 3 meters per second faster every second.
The quid pro quo is this. While the vehicle can still be accelerating (going faster) but (and here’s the important bit) not adding so much speed to the existing speed every second. When the rate of acceleration starts to slow and continues to slow it means that car will soon be travelling a constant speed or flatten out.
That is where China is right now, they have almost flattened out i.e. their vehicle has almost reached a stable speed and will soon be starting to lose speed.
China started its lockdown on 23 January (beginning of this graph). Only on 14 February did the curve start to flatten. So slowing down is massively important
For the first time in a week, our rate of acceleration has slowed down. Yes, our car is still picking up speed and yes unless the rate of acceleration slows down, even more, we are still heading for a disaster, but we have slowed down.
I was equally encouraged on the 21st and 22nd when our rate of acceleration slowed way down, but it was weekend and I suspect the admin bit of our testing regime let to a lag in reporting so that it was a false reading. I am hoping like hell that today’s news is a not a false reading too.
The exponential growth in the context
The easiest way to understand this whole exponential growth curve – the curve we are trying to flatten, is to understand that exponential curves are always about doubling the value in a specific time. If the curve is steep, the time to double is short and if the curve is flat, the time to double is long.
As of today, China’s rate of doubling the number of infections 45 days, while South Africa’s is 3 days.
Below is a live-updating chart indicating the rate of doubling. Be sure to select doubling time and log scale to see where South Africa lies.
I suspect that not too long from now, countries will lose track of number of infections as they run out of tests or the number of people required to be tested simply overwhelms the system. From that point onward only the number of deaths will be recorded and we will measure the spread at the rate at which the number of deaths double.
As I write this, it is surreal to think that we are living in a time where we measure the rate at which the number of people that died doubles.
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