Our Covid testing in South Africa is going to increase. This is going to cause a "second wave" of cases, but just like the wave pool at Sun City, this wave will also be man-made.

Let me do some "CNN level" basic maths to unpack this.

The number of positive cases is predominantly a function of 3 factors:
1. The volume of testing
2. The percentage of tests which come back positive
3. The proportion of false positives

(3) is a subset of (2), but it's still important

The number of positive tests is therefore:

Volume of testing * Percentage of positives

Increasing volumes alone, with percentage positives being constant, WILL result in more cases. This is not a second wave, but purely a function of how many tests we are performing.

It's therefore critical that we watch the case positivity rate. This is harder to manipulate at high testing volumes.

At the peak of our real cases wave, the case positivity rate reached almost 30%. It's fallen steadily since. For more than a week now, it's been under 10%.

To the extent that positivity stays stable where it is, or better yet, it continues to fall - despite cases like increasing with more testing, this is NOT a second wave, and ultimately would be good news.

Don't worry though - many of us will be tracking this.

There is a non-negligible number of false positives that come out of PCR testing. It's worth bearing this in mind that we will never get to a zero positivity rate given that the (current) test itself falsely finds positive cases in relatively meaningful numbers.