Third wave covid-19 South Africa
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  • South Africa's third wave of Covid-19 has been particularly bad in Gauteng, with hospital admissions and deaths exceeding those recorded during the second wave.
  • But on a national level, South Africa's third wave is still less severe than the second.
  • This was predicted by the South African Covid-19 Modelling Consortium back in April, although it didn't account for the Delta variant.
  • This scenario was forecast by the Actuarial Society of South Africa, which says it is "still closer to the middle road than the worst case."
  • But civil unrest in South Africa’s most populous provinces has all the hallmarks of a superspreader event which could reverse the wave’s downward trend. 

South Africa's third wave of Covid-19 infections has surpassed previous surges in terms of the sheer caseload recorded over the past month. And, while the impact on Gauteng has been worse than expected, pre-emptive modelling based on national hospital admissions and deaths shows that South Africa has avoided a worst-case scenario where deaths far exceed those recorded in the second wave.

The seven-day rolling average of Covid-19 cases has started to decrease, indicating that South Africa may be over the peak of the third wave. This, however, does not correlate directly to the mortality rate – which determines the veracity of the surge – in real-time and deaths associated with peak infections are expected to increase over the next few days or weeks.

Increasing positivity rates, which measure the number of people who test positive for Covid-19 in relation to the number of tests conducted, are commonly used to indicate the presence of a new wave of infections.

South Africa's first wave, between July and August 2020, had a peak positivity rate of around 27%. The second wave, between December and January, was recorded at 33%. The third wave's positivity rate breached 31.4% on Monday, according to the National Institute for Communicable Diseases (NICD).

Previous waves, marked by a rapid increase in infections and deaths which align with a burgeoning positivity rate, have lasted for about six weeks. South Africa officially entered the third wave on 10 June, as announced by the NICD.

At the height of the second wave, Gauteng recorded a seven-day rolling average of Covid-19 cases of around 5,500, similar to that experienced during the first wave although with a steeper drop-off. This rolling average doubled during the third wave, with the peak being recorded at close to 12,000 daily infections, accounting for more than half of the national caseload.

Similarly, hospitalisations and deaths in Gauteng exceeded those recorded in the previous waves.

This was predicted by the NICD’s South African Covid-19 Modelling Consortium, which noted, back in April, that a slow and weak response to the third wave would have devastating consequences in Gauteng.

"Our provincial projections show substantial variation of the size of the third wave between provinces, reflective of different age distributions and prevalence of comorbidities, with the third wave being highest in Gauteng across all scenarios, due to the higher concentration of working-age adults and people with co-morbidities in the province, and the lower estimates of seroprevalence," the modelling consortium noted.

The NICD's modelling also predicted that, on a national level, the peak of the third wave was expected to be lower than the second wave. It warned, however, of two key variables which could lead to a wave worse than the second, namely, the detection of a new, more transmissible variant and a delayed response from government in implementing harsher lockdown restrictions.

This scenario played out with the detection of the Delta variant, which has been driving infections since May, and government heightening lockdown restrictions from mid-June, at a time when Gauteng's positivity rate had already breached 20%.

Despite a new variant and a delayed response from government, hospital admissions and deaths have, on a national level, been higher than the first wave but lower than the second wave.

"We believe that it is still closer to the middle road than the worst case," Adam Lowe, member of the Covid-19 Working Group of the Actuarial Society of South Africa (ASSA), told Business Insider South Africa.

The ASSA did its own modelling on the potential of a third wave in early May and detailed three scenarios. A third, less severe wave in May was listed as the most likely scenario. A delayed wave peaking in late winter was regarded as less likely but more severe and a sudden surge, driven by super spreader events and a new variant, was noted as the worst-case scenario.

"In terms of these three scenarios we put out, we seem to have landed pretty close to the second one, namely a delayed, more severe third wave… However, there are also elements of the third scenario present, notably due to the rapid spread of the Delta variant and a very heavy case load in Gauteng," said Lowe.

"This points towards lower immunity than we might have expected at the time of putting the release out."

The NICD predicted that a slow, weak response by government could result in around 100,000 hospital admissions being the worst-case scenario accounted for in the modelling. Over the past month, the NICD has recorded more than 40,000 hospital admissions throughout the country.

Barring a sudden resurgence in Covid-19 cases – something which wasn't witnessed after the peaks of previous waves – it seems unlikely, based on both the NICD and ASSA modelling, that South Africa's third wave will realise a worst-case scenario of far exceeding deaths experienced in previous waves.

"The current thinking seems to be that the peaks in KwaZulu-Natal and the Western Cape in particular will not be as bad as Gauteng but it is too early to tell," said Lowe.

But recent unrest in KwaZulu-Natal and Gauteng – which together account for almost half the country’s total population – have the potential to trigger a resurgence. Epidemiologist Professor Quarraisha Abdool Karim said that the riotous looting in the two provinces, which forced thousands of people into confined spaces with little regard for social distancing or mask-wearing, was a “recipe for superspreader events”, according to News24. This kind of superspreader event, noted by Lowe in the ASSA’s third wave modelling, could prove to be the perfect storm.

“This virus is spread by movement and physical contact between people and anything that mitigates that contact, assuming people adhere to the lockdown regulations, and the protests are an example of people not adhering it, should have an effect on dampening the virus,” explained Lowe, noting that while Adjusted Alert Level 4 restrictions came too late for Gauteng, limiting movement in the coastal provinces would likely subdue the national caseload.

“Our worst case was Easter and the holidays surrounding it acting as a superspreader ‘seed’ event allied with lower than expected immunity levels.”

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