ANALYSIS | The big problem with South Africa's official Covid-19 numbers
103 deaths. 5 350 cases. 197 000 tests. 6 million screened. One problem. Is the data reliable? asks Kyle Cowan
On Thursday evening last week president Cyril Ramaphosa gave his sixth live, televised address to the country around the Covid-19 pandemic.
With his hallmark and now almost familiar measured and impactful tone, he reiterated the seriousness of the effects this coronavirus could have on our country.
He spoke of unification in the face of an unprecedented struggle as he announced a new risk-level approach to easing lockdown.
“To date, over 2.6 million confirmed cases have been reported worldwide. The actual number of people infected is likely to be far higher,” he said.
By Friday morning, that number had topped 3 million. But Ramaphosa made it clear - the official numbers in South Africa, and the rest of the world, was probably not the whole picture.
Scientists and epidemiologists agree.
In the past weeks a new way to track deaths during the pandemic has emerged, with varying results. Researchers and scientists are looking to death registries - records kept of deaths in every country - to determine true mortality rates.
The data when looked at over several years can provide expectations of what deaths would look like in the future across geographic areas and can be classified by age and compare that with deaths reported as confirmed Covid-19 cases and go further – compare the total number of deaths in the same time period with what was expected.
The New York Times reported this week that in New York City, the epicentre of the US outbreak, 20 900 ‘excess deaths’ (deaths above what was expected) were reported since the start of the Covid-19 outbreak in the city.
The Financial Times conducted a similar analysis over several countries, and found the death rate could be 60% higher than what is officially being reported.
A comparison of the confirmed and reported infection rates of South Africa and other countries in Africa.
The reason for this is explained in interviews News24 recently conducted with Professor Cheryl Cohen, a top epidemiologist and co-head of the Centre for Respiratory Diseases and Meningitis at the National Institute for Communicable Diseases.
It is centred on one central theme with several factors - under detection.
"There are two levels of under-detection. There is a level of under-detection where we understand we have symptomatic people who have fever and cough, they may be mild, they may be more severe, they may be in hospital, and we accept that we may not be catching and testing all of them," Cohen said.
That number could be as high as one to 10 per confirmed cases, some studies have shown. Other studies have shown higher levels.
"I would say that it is generally accepted that we are missing some of the cases, but it is very difficult to quantify to what degree that is. It is based on probabilities, it is likely that when we had that huge wave of importation from overseas, there would have been additional importations that would have gone undetected and once those importations spread to additional people, it would have been very hard to find them in the ocean of respiratory disease that we find ourselves in as we go into the winter season."
Cohen previously said the second issue around under-detection was the issue of asymptomatic cases.
"It is an emerging area of research, only in the last week or two a whole host of studies have started coming out, all pointing to the same thing, the same idea that there is likely a large pool of cases, I don’t know how large, but some people are saying that up to 70% of cases could be asymptomatic or mildly symptomatic," Cohen said.
Analysis of mortality data by the South African Medical Research Council and the University of Cape Town's Burden of Disease Research Unit shows that as of 21 April, deaths in the country are still tracking within expected bounds. But this is likely to change. Source - SAMRC/UCT Burden of Disease Research Unit.
"That’s something that is going to have to be considered by mathematical modelers in SA and around the world, but it’s quite new, the evidence for that has only come out quite recently and that will, I think, be the emerging story."
She said there was evidence that asymptomatic people can transmit Covid-19, but they would likely transmit at a lower rate than symptomatic cases.
"The question then is how impactful are they on a population level? That’s the difficult part."
The problem becomes compounded when it is taken into account that testing every single person in South Africa is just not possible.
On 29 April, the department of health reported that 197 127 tests had been done so far by public and private laboratories. But, this is since late February.
The first confirmed case was announced on 5 March.
On 28 April, the total number of tests done stood at 185 497 – so in a day, across all laboratories, South Africa conducted 11 630 tests for the coronavirus.
When paired with a massive community outreach screening and testing programme - possibly the largest in the world - the numbers of tests are expected to increase, and therefore the number of positive cases.
But until a large percentage of the 56 million people living in the country are tested, it is almost impossible to say for certain how widespread the coronavirus is.
Screening being conducted now is crucial but does not solve the problem of asymptomatic spreaders - because the screening focuses on finding people with symptoms fever, sore throat, cough and shortness of breath – and refers them for testing.
Asymptomatic Covid-19 carriers may slip through this net.
A comparison between tests conducted by public and private laboratories as of 28 April 2020.
The data reported by the Department of Health on a daily basis is therefore accurate, in the sense that it reflects the verifiable testing data available to the department.
But the cautionary tale is in the mortality data emerging around the world.
News24 reported this week that here at home the South African Medical Research Council and the University of Cape Town’s Burden of Disease Research Unit has started tracking this data for South Africa.
The unit’s latest report, released on Wednesday, shows that South Africa’s overall death rates are still tracking in the expected bounds, but the lockdown has prevented a large number of unnatural deaths.
It is clear that with the partial easing of lockdown infections will start increasing at a more rapid rate. The question that remains is at what pace.
For now, South Africa is not seeing the high numbers of confirmed deaths or infections seen in other countries.
But, “Watch this space,” Professor Tom Moultrie, part of the UCT unit, tweeted this week.