Based on antibody testing, between 35% and 40% of South Africans have been infected by COVID-19, estimates Prof Shabhir Madhi, a member of the Medical Advisory Committee advising Health Minister Dr Zweli Mkhize.
Madhi was speaking at a Daily Maverick webinar. He said that initial infection models estimated that about 25% of the population would be infected. The high prevalence of infections did not, however, translate into high rates of hospitalisations and deaths.
Daily Maverick quotes Madhi as saying that about half of the confirmed number of cases in South Africa had been confirmed by private sector laboratories, but the private sector does not look after 50% of the country’s population. He added that the asymptomatic and mildly symptomatic also didn’t get tested. “The numbers (35% to 40%) are based on antibody testing,” he said.
He added that at the peak of the outbreak the country was reporting about 14,000 cases a day, but the new models show that there were between 60,000 and 80,000 new cases a day.
“While the number of deaths is probably an underestimate… we haven’t seen the infection rate translate into hospitalisation and deaths. It did not transpire to the extent that modellers predicted.”
According to Daily Maverick, he said that using the Western Cape as a benchmark, while there had been about 15,000 confirmed deaths caused by COVID-19 in South Africa, the actual number was likely to be about 30,000. “Not everyone who has died has been tested for COVID-19. We must appreciate that there had been many deaths outside of hospitals. If we use the Western Cape as a benchmark and use the same adjustment – we think roughly 30,000 rather than 15,000.”
Providing reasons hospitalisations and deaths were relatively low for a country that had such a high number of infections, Madhi said the theory he favours is that South Africans had an “underpinning immunity, probably because of exposure to common cold coronaviruses”. He said this would have offered a cross-protective immunity against the virus that caused COVID-19.
Other theories, Madhi said, are based on the relative youth of South Africa’s population and preventative measures, like lockdown and the wearing of masks, that could have offered some protection.
Daily Maverick reports he said, however, if the country dropped its levels of adherence to non-pharmaceutical interventions, there would probably be a resurgence. “But it will be less severe this time round.” While this was difficult to predict, as it depended on how complacent people become about masks, hand-washing, physical distancing and mass gatherings, Madhi said emerging patterns in European countries showed a surge in infections after the summer holidays. “We might see less compliance in December, meaning that come January and February we might see a resurgence.”
He added: “The reality is that people do become re-infected. There is nothing unusual about it. The reason you recovered the first time was that you developed an immune response. One of the challenges with this virus is that we do not know how long this immunity will last.”
“The best-case scenario for us is that it becomes a seasonal virus with sporadic outbreaks. It is extremely unlikely that we will get to elimination. Some of these respiratory viruses have been circulating since the 1960s. Segments of the population will always remain vulnerable. We don’t know how long immunity will last.”
He said the health consequences of lockdown must also be addressed with great urgency, explaining that about 12,000 excess deaths due to natural causes recorded this year were a consequence of stringent lockdown rules.
That this view comes from Madhi is significant, since he’s a member of the ministerial advisory committee (MAC), which advises Mkhize and the government on its COVID-19 response, writes Rob Rose in Business Day. And, if we’re closer to a situation of more widespread immunity than we think, it would provide impetus for a faster easing of the suffocating lockdown.
Rose writes that Madhi’s assessment also underscores the view of Discovery Health CEO Ryan Noach, who said last week in a presentation that his company “estimates that approximately 13m South Africans have been infected”.
Rose writes that there are some intriguing theories on “herd immunity” going around, even if Madhi thinks it’s too early to suggest SA has reached that stage just yet. He writes that in STAT News, expert health reporter Helen Branswell outlines four ways in which people could develop immunity to COVID-19.
The first is “sterilising immunity”, in which a body’s immune system simply cuts off a virus as soon as it’s detected. But the odds of this, the experts say, is low.
The second is functional immunity – in which people whose immune systems have been primed to fight the virus through prior infection or a vaccine end up having less severe and serious reinfections. This, the scientists say, is a more likely scenario.
The third option is waning immunity, where someone loses their protection over time, but subsequent reinfections aren’t likely to be that severe.
The last option is lost immunity, where later reinfections are as bad as the first – a scenario which experts say is unlikely.
Branswell writes: “If these experts are correct, and the worst-case scenario is off the table, humans can expect to see a waning of the threat (that COVID-19) poses to people over time. Our immune systems will know how to deal with it. It could become the fifth human coronavirus to cause common colds.”
The latest indicators come in a report by the World Health Organisation surge team working with the health department that shows a 42% drop in the number of reported COVID-19 cases and a 29% drop in COVID-19 deaths in the two weeks to 10 September, while the median test positivity rate fell to 9.8%, compared with 11.4% the week before, Business Day reports according to Health Minister Zweli Mkhize.
The numbers waned despite the government’s gradual lifting of lockdown restrictions, defying expectations that increased social contact would accelerate transmission, and lending weight to calls for the curfew, liquor sale controls and international travel ban to be lifted.
The consortium of modellers advising the government recently ran a scenario analysis to try teasing out the effect of possible explanations for the drop. The consortium says South Africa’s health system coped largely because the epidemic took off later than in many other countries and surged at different times in different areas. That enabled doctors to take advantage of improvements in patient care as evidence emerged of the benefits of the steroid dexamethasone, placing patients on their stomachs, and high-flow nasal oxygen.
The relatively young structure of the population has also helped, it says, because while age does not affect susceptibility to infection, it is a significant risk factor for severe disease and death. But scientists such as Madhi suggest the high prevalence of noncommunicable diseases such as diabetes and hypertension may well have offset these age gains.
Scientists say it is also possible that widespread mask usage helped reduce disease severity in many infected people by their exposure to the virus. Another possible explanation for the low mortality rate despite the high prevalence is that prior exposure to other less deadly coronaviruses – such as those that cause the common cold – provided degree of protection.
When epidemiologists first modelled their forecasts earlier this year there were fears that people, especially those in densely populated spaces, were at a greater risk of rapid infection. But Eyewitness News reports that the numbers continue to tell a different story.
While research is ongoing, early studies were published to support how these so-called memory T-cells work.
Madhi – who’s also the director of SAMRC’s Vaccines and Infectious Diseases Analytics (VIDA) Research Unit and is South Africa’s lead researcher on the COVID-19 vaccine trial – said that people in high-density areas could have generated this immunity because of previous widespread exposure to common cold coronaviruses. “They have been exposed, they developed this key cell immunity which helps them to fight the severe effects of COVID-19,” he said.
“If there is a second wave we will probably see another 15 to 20% infected, then you are reaching the threshold required for herd immunity. We will then see seasonal outbreaks during autumn and winter,” he said.
The report says for a country whose earlier rapid rise of infections sparked fears of a health system collapse, South Africa’s COVID-19 mortality remained far lower at just over 1%.
South Africa’s decline in COVID infections goes against what other countries, in particular in Europe, are currently facing, says a Saturday Star report. Many are fighting a second wave of the disease, and are enforcing harder lock downs.
"The mystery is that despite so many people getting infected and with such a high percentage of the population possibly becoming infected, why didn’t this translate into severe disease or excessive numbers of deaths," says Madhi, about South Africa’s experience of the pandemic.
Professor Alex van den Heever, who holds the chair of social security systems administration and management studies at Wits University explained this high immunity to the disease didn’t have to be wide spread to limit the national infection rate.
"So, in high risk areas, where people have had difficulty social distancing and have had to use taxi transport, those communities appear to have had a high prevalence," says Van den Heever. "So maybe these very localised but very important areas have allowed immunity to build up."
The report says in the coming weeks Madhi and other researchers will be doing more testing to understand how the disease spread and to explain why so many South Africans became infected with the virus, but didn’t become seriously ill. They have yet to work out just how much of the population of Gauteng was exposed to the virus.
But still Van den Heever warns that following the protocols of social distancing, mask wearing and hand washing are still important and a change in behaviour could bring a spike in infections.
“If we started acting like we did in February, we will probably see a resurgence. But if we maintain the current protocols, we might see the continuation of the downward trend.”
Leading epidemiologist and infectious diseases specialist Professor Salim Abdool Karim said, however, that the country is not out of the woods just yet. “We are at a continued high risk and threat of having another wave. I think that is just part of the reality that we have to live with,” he is quoted in The Citizen as saying. “Data shows the country’s five key indicators were “all going in the same direction”.
Abdool Karim said that the number of cases is coming down. The proportion testing positive is coming down, the admissions, deaths, excess deaths and oxygen use is coming down. Every indicator we have is going in the right direction.
The Lancet COVID-19 Commission classified countries with a threshold of one positive case per 100,000 as having a low level of transmission, he explained, while the WHO threshold was at a 5% positivity rate.
Abdool Karim believed South Africa was “at a stage where we are beyond these levels” of lockdown. We need to move on now and say this is the new normal. We need to continue our lives, get back to doing the things we do, provided we continue our prevention strategy – hand washing, mask wearing and social distancing.
“We have to institute certain restrictions we are going to have to live with in the long term. And those are restrictions that really prevent mass gatherings that lead to super-spreading events – that what we want to avoid, a situation where one person can infect many others.”
The South African government’s swift action in imposing a hard lockdown within weeks of South Africa’s first coronavirus case will have averted 16,000 deaths by the end of the year. Business Day reports that this is according to an analysis by South Africa’s biggest medical scheme administrator, Discovery Health whose modelling projects 51,000 deaths from COVID-19 by the end of the year, a figure that would have been 25% higher if there had not been such stringent measures to curb transmission of COVID-19.
Discovery’s mortality estimates are broadly in line with the Actuarial Society of SA, which said last week that its latest model projects between 27,000 and 50,000 deaths from COVID-19 this year.
The report says the government has faced fierce criticism over the economic costs of the lockdown, which has seen businesses shuttered and massive job losses. South Africa’s approach stood in sharp contrast to that of many European countries, such as Italy and the UK, which imposed lockdowns only when hospitals were already overwhelmed.
South Africa’s restrictions on people’s movement and mass gatherings helped slow the rate of infection and spread cases out over a longer period, buying time to ramp up health-care capacity and take advantage of developments in the treatment of patients, said Discovery Health chief actuary Emile Stipp in the Business Day report.
"There are clear signs that South Africa has effectively navigated the peak of the pandemic with staggered hot-spot outbreaks resulting in longer, flatter regional peaks and lower infection fatality rates than the global experience," he said.
Analysis of claims data from members of Discovery Health’s client schemes, which include Discovery Health Medical Scheme, showed the mortality rate among COVID-19 patients admitted to an ICU had improved by 25% since the start of the pandemic, dropping from 80% to 60%, said Stipp.
[link url="https://www.dailymaverick.co.za/article/2020-09-14-covid-19-may-have-already-infected-20-million-in-south-africa-says-prof-madhi/"]Full Daily Maverick report[/link]
[link url="https://www.businesslive.co.za/fm/opinion/2020-09-14-rob-rose-are-you-one-of-the-35-of-south-africans-whove-had-covid-19/"]Full Business Day report[/link]
[link url="https://www.statnews.com/2020/08/25/four-scenarios-on-how-we-might-develop-immunity-to-covid-19/"]STAT News report[/link]
[link url="https://www.businesslive.co.za/bd/national/health/2020-09-16-sas-waning-covid-19-epidemic-puzzles-experts/"]Full Business Day report[/link]
[link url="https://ewn.co.za/2020/09/14/south-africans-covid-19-immunity-caused-by-exposure-to-previous-coronaviruses"]Full Eyewitness News report[/link]
[link url="https://www.iol.co.za/saturday-star/news/joburgers-could-have-reached-herd-immunity-without-even-knowing-it-experts–03f47b1f-2638-43df-8daf-47f023ab960c"]Full Saturday Star report[/link]
[link url="https://citizen.co.za/news/covid-19/2358668/sa-at-a-stage-where-we-are-beyond-these-levels-of-lockdown-says-abdool-karim/"]Full report in The Citizen[/link]
[link url="https://www.businesslive.co.za/bd/national/health/2020-09-10-lockdown-could-end-up-saving-16000-lives/"]Full Business Day report[/link]
See also
[link url="https://www.medicalbrief.co.za/archives/expert-estimates-of-sas-pandemic-deaths-plummet-again/"]Expert estimates of SA’s pandemic deaths plummet again[/link]