Since the lockdown regulations eased to Level 4 and many people return to work, the authorities are ever watchful as to how this will affect community transmissions. And while President Cyril Ramaphosa cautions in his latest newsletter that we should change our behaviour as we prepare to continue living with the coronavirus for a year or even more, retired actuary Dave de Klerk continues playing around with different types of analyses from the very extensive, real-time coronavirus data www.worldometers.info provides. In his latest analysis he takes a closer look at why the Western Cape, with only 12% of the country’s population, makes up just over half the whole country’s positive cases. – Editor
By Dave de Klerk*
Even though, on the surface, the global comparative Covid-19 figures look good for South Africa, they hide the situation occurring in the Western Cape, which is much worse than the national average based on the criteria set out below.
Table 1 updates last week’s international comparisons.
In column A most countries’ ratios of cumulative positive cases to cumulative tests done, has reduced over the last week as they presumably reduce their infection rates. South Africa has increased slightly from 2.7% to 2.9%.
As ongoing deaths occur, in virtually all countries, the deaths per million populations shown in column C also increase. South Africa has increased from 2% to 3%.
For most countries the ratio of cumulative deaths to cumulative positive cases has remained fairly constant over the past week, the additional percentage of cases found roughly cancelling out the additional percentage of deaths. South Africa increased slightly from 1.9% to 2.0%.
To put these South African figures in context, the whole world’s average deaths per positive cases found is 6.8% (280,443 deaths out of 4,101,772 cases) and these deaths per million population average 36.
Table 2 provides a further breakdown of the South African figures.
As will be seen, if the Western Cape is excluded, South Africa’s figures look even better than those shown in Table 1. Over the past week the ratio of cumulative cases to tests in fact went down from 1.9% to 1.7% – only bettered in Table 1 by South Korea, Australia, UAE, Thailand and New Zealand.
If you look at the provincial breakdown of positive cases which have been “found” in our nine provinces, you again see that the Western Cape makes up both a much higher number of cases per million of (provincial) population, as well as just over half the whole country’s positive cases (but with only 12% of the country’s population).
This could be interpreted in different ways.
If you look at the number of tests done, the Western Cape has done 57,840 out of a national total of 324,079 or about 18%, but has about 12% of South Africa’s population. If you assume that 50% more tests might “dig up” 50% more positives, you still don’t come close to explaining the Western Cape having half the country’s cases.
It has been suggested that testing may not be as rigorous in some of the other provinces, but deaths arising from Covid-19 presumably are being accurately recorded throughout the country. Based on this statistic the Western Cape has had just under half the deaths from 12% of the population. However the ratio of deaths to cumulative positive cases in the Western Cape is not too different from the rest of the country. In both cases about 2% have died (so far? ).
So it does look to me as if there are probably significantly more infected people in the Western Cape than in the rest of the country, but based on admittedly a small sample, their mortality once tested positive is no higher than in the rest of the country.
Within the Western Cape it also looks as if the Cape Town Metropole is significantly more infected than the rest of the province based on cases found per number of people living in each area.
- Dave de Klerk is a retired actuary living in, or rather locked in, Cape Town.