How do we know if SA is in a third Covid-19 wave  and could there be a fourth?
South Africa is on the cusp of a third Covid-19 wave, with some provinces already there. The country hasnt vaccinated nearly enough people for its vaccination roll-out to make a difference to the potential severity of this wave, experts have warned. By Sunday, only 479 768 (0.96%) of South Africas population of about 60-million people had been fully vaccinated, and 870 477 had received one of two shots of Pfizers Covid vaccine. According to the former chair of the Covid ministerial advisory committee (MAC) Salim Abdool Karim, a country would need to vaccinate well over 70% of people of 60 and older to reduce deaths and hospitalisations significantly. South Africa, therefore, only has the natural immunity of those who have had Covid caused by the Beta variant, which is the main form of the virus circulating in South Africa, as well as adherence to mask-wearing, social distancing and hand-washing, to rely on. Well, theres a formula, which was developed by our modelling consortium and adopted by the MAC. Bhekisisa and Media Hack explain how the formula works and apply it to each province to make it easy to understand where were at. We also spoke to Abdool Karim to break down the factors that will influence how South Africas third wave plays out, how long it will last and whether  and when  well see a fourth wave. The South African Covid-19 modelling consortium developed a formula that the health department uses, at the recommendation of the MAC, to calculate whether the country or a province has entered a new Covid wave. The formula says a Covid wave starts when the seven-day moving average of new cases exceeds 30% of the peak of the previous wave. A moving average means that youve taken numbers for each of the seven days selected (in this case new Covid cases), added them up and divided them by seven to get the average of those days. You would then plot them on a graph, so that it helps you to see what new cases look like over time (instead of plotting daily numbers, which may sometimes vary widely and be confusing to interpret). Lets apply this formula to the current seven-day moving average of both national and provincial cases and see where were at. On 6 June the national seven-day rolling average of daily cases was 4 820. At the peak of the second wave (blue line) it was 19 042, which was reached on 11 January. The average daily cases on 6 June is 25% of the peak of the second wave. So, technically, by the criteria being used, South Africa isnt yet in the third wave. But, at the peak of the first wave (red line), which was on 19 July 2020, the seven-day rolling average was 12 584 cases. The 4 820 cases on 6 June are 38% of the peak reached in the first wave, so by that measure, we are now in the third wave. In other words, whether the country is in the third wave depends on which of the first two waves is used as the baseline. The third Covid wave has begun in four provinces, according to the MACs formula: the Northern Cape, the Free State, the North West and Gauteng. The Northern Cape has been the worst hit. Its third wave began in about the middle of April and the average daily cases reached a peak of 431 on 25 May, which was much higher than the peaks of the first and second waves in the province. By 6 June they appeared to be starting to decrease. The Free States third wave also seems to have passed its peak. Average daily cases began to rise in the province in April and reached a peak of 502 on 1 June. This is just 56 cases short of the peak of wave two, 558 cases, on 16 January. Covid cases are still on the rise in the North West. The 427 average daily cases on 6 June were 56% of the peak of the second wave of 768 cases on 13 January and 73% of the first wave peak of 588 on 13 July 2020. So, the third wave has begun. A third wave has also started in Gauteng. On 6 June the average daily cases of 2 531 were 48% of the peak number of 5 291 cases of wave two on 12 January and 47% of the first waves peak of 5 386 cases on 15 July 2020. Average daily cases in the other five provinces are starting to pick up, but they are some way off a third wave. In the Eastern Cape, on 6 June, the average daily cases were 7.5% of the second waves peak and 6% of the first waves. In KwaZulu-Natal they were 3% of the peak of the second wave and 6% of the first wave. Limpopo barely had a first wave, but the average daily cases on 6 June were 8% of the peak of the second wave. In Mpumalanga, the average daily cases on 6 June were 19% of the peak of the provinces second wave, but 32% of the peak of the first wave. So by the first waves standards, the province is now in its third wave, but not by the second waves standards. In the Western Cape, the average daily cases on 6 June were 12% of the peak of the second wave, but 25% of the first waves peak. The three provinces that have shown sharp increases in their average daily cases so far (the North West, the Northern Cape and the Free State) have relatively low populations, so they havent had much of an effect on the countrys national numbers. But now that the new confirmed cases in Gauteng, which has the highest population in South Africa, have started to rise, the national curve has begun to rise more steeply. KwaZulu-Natal, the second-most populous province, is still reporting relatively low daily case numbers, but if that changes, so will the national picture. And the same will apply if the daily cases in the Western and Eastern Cape, which have the next highest population numbers, begin to rise sharply. The MAC has also come up with a formula for the end of a Covid wave. The formula says when the seven-day moving average is 15% or lower than the peak of the previous wave, the wave has ended. According to this formula, the third wave hasnt ended in any province. But in the Northern Cape, its slightly more complex than that. In that province, the third wave is significantly higher than the previous two waves, so its difficult to use the previous wave (wave two) as a measure of whether the current wave is ending. On 6 June the average number of new cases was 30% higher than the number at the peak of the second wave and 44% higher than the peak of the first wave. However, the average daily cases on 6 June were 12% lower than they were on 25 May, so there is some good news in that. Abdool Karim says very few countries use formulas such as South Africas to determine if a new wave has emerged. Instead, they collectively interpret three measures: the number of new Covid cases, the test positivity rate (the proportion of tests that are positive) and hospitalisations. If the new cases, the number of tests (which is an indication that infections are increasing, because more people are coming forward for testing) and the positivity rate have all been steadily increasing, there should be reason for concern, particularly when the test positivity rate has exceeded 5%, which the World Health Organisation says is a sign that the pandemic is no longer under control. South Africas seven-day moving average for its test positivity rate was 12.7% on 6 June. Abdool Karim says that, based on seroprevalence estimates, only 10% of overall Covid cases are officially reported. For every case, we know that there are nine other cases that we dont know about, because theyre asymptomatic and such people are unlikely to have gone for a test, because they probably didnt even know they had Covid, he says. So that means, as a rough guide, if we have one new Covid case per 10 000 people, the infection rate is one per 1 000 people. In other words, the infection rate is 10 times higher than the case rate.  Hospitalisations, Abdool Karim says, always lag about two weeks behind new cases, because it takes between 10 and 14 days for an infection to show up on a PCR test and then a few more days before the patient needs to be hospitalised. South Africas first wave lasted about three months (from June to early September 2020), as did the second wave (from mid-November 2020 to mid-February 2021). The gap between the first and second waves was also about three months. But Abdool Karim says we cant tell how long the third wave will last by simply looking at the duration of the first and second waves, because we dont know if the third wave will follow the same trajectory. How long the third wave will last will depend mainly on how long it takes before the Gauteng epidemic spreads to the three other populous provinces and whether a new variant, especially one that can evade immunity, begins spreading. This will depend on a number of factors, says Abdool Karim. For one, variants will play a significant role. If we get a new variant, there are no predictions we can make, because we dont know how it will behave, he says. But if the Beta variant [also known as B.1.351 or 501Y.V2], which is currently our dominant variant, and which was also the dominant variant in the second wave, is the main form of the virus that drives our third wave, then a proportion of people who got infected in the second wave will be protected during the third wave [depending on how long their immunity lasts].  Two other variants, the Alpha variant (also known as B.1.1.7 and first detected in the UK) and the Delta variant (also known as B.1.617.2 and first detected in India) have also been detected in South Africa. The variant dominating our third wave will be the one that has the most effective combination of mutations to give it the functional advantage of transmitting faster, says Abdool Karim. We know that the Alpha variant transmits faster than the original form of the virus, and this variant has been found in the Northern Cape and Free State, where third waves have reached their peaks. But the Alpha variant doesnt spread faster than the Beta variant. And the Delta variant weve only seen in sporadic cases in South Africa, so we havent seen much in terms of local transmission.  The Alpha and Beta variants will, therefore, have to fight it out to see which one of them can transmit faster and come to dominate our third wave. My guess is that Beta will win because its a much more mutated virus and better adapted for survival. In simple terms, the Beta variant is far more scary than the other two variants, Abdool Karim says. How people behave during this wave  how well they adhere to mask-wearing, hand-washing and social distancing  will also influence how severe our third wave is, because it will affect how fast the SARS-CoV-2 virus, which causes Covid-19, spreads. Abdool Karim says we will almost certainly have a fourth wave and we can likely expect this to happen in December. We wont be able to stop a fourth wave, because you have to have a very high level of vaccination to stop a fourth wave. Youd have to vaccinate 70% to 80% of the population, which we would not likely achieve in time, he says. But it will likely be a small, mini fourth wave.  He says by the time that South Africa has a fourth wave, the country will have a better idea of whether new variants have emerged and whether the new forms of the virus are able to escape immunity and make vaccines less effective. Immune-escape variants worry me, because they could lead to vaccinated people being at risk again. Abdool Karim says: Its not necessarily critically important that we get to the governments goal of vaccinating 40-million people by then, its more important that we finish phase two [people of 40 years and older and those living in congregate settings] before December, because the people targeted in phase two are the ones who are going to get sick [research shows older people are more likely to fall severely ill from Covid than younger people]. When cases are increasing fast, as they are right now, the chances of having a Covid-positive person in a group of people, increases significantly. The moment you have a positive person in a group, you put the whole group at risk of infection, Abdool Karim says . Heres why. Abdool Karim says research shows that about 80% of new SARS-CoV-2 infections occur from only 10% to 20% of infected people. So its a very small group of people doing the transmitting. In a group, particularly in groups that get together indoors, it just takes one or two people to be positive and infect most of the rest of the group.  That is why it is so important for us to overcome peoples complacency regarding wearing masks, washing hands and practising social distancing. A formal way to deal with that is to increase lockdown levels to control group gatherings, which sends a message that factors driving the spread of the virus have intensified. Curfews influence the amount of time that people are able to socialise indoors in groups in the evenings in, for instance, restaurants and pubs, which, in turn, reduces the opportunity for infection. The short answer: Because it leads to confusion and is impractical. The longer answer: Abdool Karim says provinces are generally between two weeks and a month ahead or behind each other in terms of infections. Because we dont have a way to isolate provinces from each other (so that infections dont spread from one province to another), the infections will inevitably spread from one province to another. Youll, therefore, end up chopping and changing the rules all the time, and it all just becomes too complicated. So it makes sense to just have one set of rules for the entire country, especially because we dont have rigid lockdowns any more, so it doesnt impact the same way on business, he says. The banning the sale of alcohol has two main benefits: it decreases indoor social interactions and it reduces the number of vehicle accidents and interpersonal violence, which, in turn, frees up hospital beds for Covid-19 patients. Abdool Karim says because the main advantage of alcohol sales restrictions in a wave is the freeing up of beds, were likely to see restrictions on alcohol sales  such as limitations on the hours of sale  when hospital beds are filling up. In Gauteng, the Free State, the Northern Cape and the North West, hospital admissions have been rising for the past few weeks, according to the National Institute for Communicable Diseases daily hospital surveillance report. Admissions in the Western Cape are also starting to rise. This story was produced by the Bhekisisa Centre for Health Journalism. Sign up for the newsletter.