When the third wave hits SA, and it probably will, what will it be like?

The ministerial advisory committee is working on plans to deal with a third wave of Covid-19, while scientists try to figure out what the next variant might look like.

This is according to committee head Prof Salim Abdool Karim, who said: “Based on what we have seen so far with the second wave in SA and third wave in about a dozen countries so far, it is very likely we’ll have a third wave here.”

How a third wave plays out will be “fundamentally dependent on whether we have a new immune-escape variant then. We are busy in the lab here trying to work out what the next variant will look like based on some fascinating experiments that Prof Alex Sigal [director of the KwaZulu-Natal Research Institute for Tuberculosis and HIV] is doing.”

Abdool Karim said there was more than a 50% chance of a new variant, in which case a third wave would be “substantial”.

He added: “If we only see minor mutations without significant immune escape, then the third wave may not be as severe. Our levels of naturally induced immunity from the first and second waves will play a part in this.”

Prof Marc Mendelson, an infectious disease expert at the University of Cape Town (UCT), described the timing and scale of the “inevitable” third wave as “the million-dollar question”.

While “nothing is definite”, he pegged late autumn (May-June) as the most likely time of inception. “Factors include any relaxation of public health restrictions, particularly mass gatherings; levels of compliance with social distancing and masking; avoidance of poorly ventilated spaces; hand hygiene; and isolation of the sick.”

According to Prof Shabir Madhi, a vaccinologist at Wits University who is working on Covid-19 clinical trials, there is “reasonable probability” of a resurgence, “especially since infection with the original virus does not confer protection against infection (including mild or moderate Covid-19) with the variant”. 

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Like Mendelson, he said the magnitude of the wave would depend on behaviour, regulations “and how the virus continues to evolve”, and the “best guess” for the timing of a third wave would be “as we head into the winter period in May to June and more people gather indoors”.

It is, however, not possible to compare it to the first or second wave, with citizens and scientists smarting from the pain of a second wave that caught everyone off guard.

“The appearance of the new variant just as the second wave was building came as a bad surprise and probably contributed to its enormous extent,” said Prof Wolfgang Preiser, a virology expert at Stellenbosch University.

173,590: Active cases at the peak of SA’s first wave, on July 20 2020

33,753: Active cases on November 12, when they reached a low point

239,799: Active cases at the peak of the second wave, on January 11

44,911: Active cases on Friday

—  The numbers

“What we don’t know is the extent to which there’s a degree of population immunity, which may reduce the impact of subsequent waves,” he said. “One would hope that it could be so. Khayelitsha, for example, was badly affected during the first wave, but less so during the second wave, which suggests some protective effect (almost half the people tested had antibodies as evidence of prior infection).”

Abdool Karim said an analysis of our first two waves, as well as third waves in other countries, indicated there is generally three months between waves, but with “high variability”, and that it also depends on what you mark as the start and end of a wave.

He said when per capita active cases reach five per 100,000 a day, it is considered a threshold for low transmission and generally correlates well with a low proportion of positive tests.

“Based on these data and if the virus continues behaving as it did up to now, we can expect our third wave in roughly June-July. This timeline also coincides with the change in behaviour during our winter, where more people are indoors without open windows,” he said.

“The variants create a new level of uncertainty: uncertainty on the efficacy of vaccines and uncertainty on future epidemiological patterns of the virus. But despite this uncertainty, we can work with the likely scenarios and prepare for a possible severe third wave in mid-2021.”