- Coronavirus cases in South Africa are growing at a higher rate than any other country in the world when compared by infections per 100 000 people.
- As the global death toll continues to rise, SA's Covid-19 mortality rate continues to be among the lowest in the world.
- A lower testing rate and high growth rate mean SA could have a high number of cases going undetected until patients arrive at hospitals seeking care.
South Africa is now recording new coronavirus cases every day at a rate higher than any other country in the world when reported Covid-19 infections are compared by population size.
On average for the week of 6 to 13 July, the country recorded 19.6 cases per 100 000 people – a growth rate higher than every other country in the world currently.
The calculation is made by taking the daily case increases over time and finding the proportion per 100 000 people of the population these daily new cases represent. To make sense of this visually, this daily case increase per 100 000 people is then placed on a seven-day rolling average scale, as seen in the graph below.
It is clear from the graph that on this seven-day rolling average, only Peru has historically exceeded an average rise of more than 20 cases per 100 000 people a day. The daily increase rate in Peru, while still significant, has declined steeply in recent weeks when compared with other countries.
Comparatively, SA is testing at a lower rate than other countries – which gives rise to fears there are a high number of cases that remain undetected. When testing per day is mapped on a similar seven-day average of tests per 100 000 people, it is clear that testing in South Africa is outpacing many of the "top 10" countries with the highest cumulative infections, but lags behind countries that have found a similar number of cases, such as the United Kingdom.
On Tuesday, SA also overtook the UK in terms of cumulative confirmed Covid-19 cases with a reported 298 292 cases, which means it is now 8th in the world in terms of the most cases recorded over time.
As of Tuesday, UK health authorities reported 291 393 confirmed cases.
The surge in cases in SA in July has been driven by significant increases in cases in Gauteng, which became the first province to record more than 100 000 coronavirus cases at a case doubling rate hovering around 10 days, compared with more than 20 days in the Western Cape, where the majority of the country's cases were initially found.
Low testing numbers in SA mean a high number of cases could potentially be going undetected. As of Tuesday Health Minister Zweli Mkhize reported that 2.2 million tests had been conducted for Covid-19, translating into roughly 3 864 tests per 100 000 people – lower than Chile, the US, the UK and Russia.
As of Tuesday, SA had conducted 5 million tests less than the UK, but found more cases.
While the overall testing strategy for South Africa remains unclear, in June Mkhize confirmed to News24 that the country was moving toward a more targeted testing strategy which would focus on hospitalised patients and close contacts of confirmed cases, as well as healthcare workers.
This means that testing is not giving a clear picture of the actual spread of Covid-19, and scientists generally accept there is a high rate of underdetection of cases which is yet to be quantified.
Stat News reported in early June a top World Health Organisation (WHO) official clarified that scientists had not determined yet at what rate asymptomatic cases spread the virus just one day after suggesting that such spread is "very rare".
The clarification came after the WHO's "original comments incited strong pushback from outside public health experts, who suggested the agency had erred, or at least miscommunicated, when it said people who didn't show symptoms were unlikely to spread the virus", Stat News reported.
A recent study published by the National Academy of Sciences by scientists in the US found "that silent disease transmission during the presymptomatic and asymptomatic stages are responsible for more than 50% of the overall attack rate in Covid-19 outbreaks".
The latest available modelling by the SA Covid-19 Modelling Consortium also estimates a high level of undetected cases – possibly 3 million cases being detected out of 12 million infections over time.
But the modellers have repeatedly warned the estimates should be interpreted with caution due to a "high degree of uncertainty" surrounding reported coronavirus data.
Access to detailed Covid-19 data collected by the Department of Health has been severely restricted and only basic data is made public, but based on available public data the increase in the percentage of tests coming back as positive for Covid-19 has also steadily increased in recent weeks.
The South African Health Products Regulatory Authority recently approved the country's first serological rapid test kit, which could significantly amplify efforts to find Covid-19 cases.
But crucially, the country has recorded 4 346 deaths compared with the UK's 44 915 deaths (as of 14 July) and has one of the lowest crude mortality rates globally.
The explanations offered by scientists as to why the death rate is so low compared with European countries has varied – but a leading theory is that Covid-19 is yet to spread to vulnerable communities where access to healthcare and living conditions do not provide opportunity for social distancing.
South Africa also has a comparatively young population, and death trends observed in other countries and here show older people are at higher risk of falling seriously ill from the Covid-19 disease.
On Sunday, President Cyril Ramaphosa urged the country to behave responsibly and prove models wrong that estimated the country would experience 40 000 deaths from Covid-19 over time.
*The headline of this story was corrected after publication to clarify that the increase in cases in South Africa is at the highest rate in the world, not outright infections. The error is regretted.