Modelling the progression of the pandemic involves complex data and a wide range of disciplines. It’s a far from exact, often flawed, business, but the alternative is confusion and conspiracy theories, writes Fatima Khan
First published in The Witness
Social media and other news feeds can be disquieting at times, but the Covid-19 crisis with its avalanche of information has swung the anxiety meter for many into the red.
The public is being exposed to statistics and sometimes sophisticated modelling that it often lacks the formal training to digest.
Amid the resulting confusion, it’s a small wonder that more conspiracy theories haven’t taken root.
How to sift fact from fiction and disinformation?
Presenting the most reliable data in a more palatable fashion might help.
Ridhwaan Suliman, a senior researcher at Council for Scientific and Industrial Research (CSIR) with a background in mathematical modelling, has made it his personal project to try to do just that.
Suliman has taken to tweeting immediately after the National Institute for Communicable Diseases releases its daily Covid-19 figures.
He had been following the official updates for some time and felt the raw numbers, particularly in isolation, might be hard for much of the public to swallow.
Working from his home under lockdown, Suliman, a cricket and Formula One fan, quickly turns the official numbers into graphs that are easier to follow.
He started analysing the data after Professor Salim Abdool Karim, the epidemiologist and chairman of the Covid-19 ministerial advisory committee, gave a presentation on national TV on 13 April. Karim told the public that lockdown has been effective but the country could not escape a “flood of infections”.
Conspiracy theories don’t bother Suliman much, but he feels people will be able to deal with misinformation better if armed with the facts. He wanted to show how the figures could provide an unbiased and more complete story.
He was reluctant to make predictions about the course of the pandemic in South Africa, stressing he was not a medical doctor nor an epidemiologist.
However he noted, “While there was a surprising lull in Covid-19 cases in South Africa immediately after lockdown, with the increasing number of tests over the last couple of weeks we are now seeing a more realistic increase in the number of confirmed cases.”
Suliman said the number of Coronavirus tests yielding positive results had remained relatively constant over a long while, between 2.5 – 3%. But on 12 May spiked to 5.1%, the highest since lockdown began.
“We are all afraid of the unknown and I hope that by sharing correct information this can alleviate the fear that this pandemic has brought about,” he said.
Not so fast
Cape Town biostatistician, Professor Maia Lesosky welcomed efforts to present the official figures in a clear format but felt this alone gave a limited picture.
Context was king.
“We are bombarded daily in the media with a counter for the global and country by country increase in the number of cases,” said Lesosky who was attached to the Division of Epidemiology and Biostatistics at the School of Public Health and Medicine at the University of Cape Town.
A country’s testing strategy made a big difference to the case count it arrived at and any conclusions drawn about the spread of the disease.
For example, she said, a country could:
- Do no testing;
- Test only the very sick that come to hospital with Covid-19 symptoms;
- Test the people with whom the very sick people had had some contact; and
- Test everyone.
Each strategy led to different conclusions about the spread of the disease, even though the true number of infected people remains the same.
Dead simple, not…
You might think mortality rates were simple, but again the quoted figures sometimes fail to give the full picture.
Countries have taken very different approaches to reporting mortality rates.
“Definitions of Covid-19 deaths have ranged from including only confirmed SARS-CoV-2 positive individuals all the way to including anyone who died in a nursing home while the epidemic was occurring.”
Other countries have said only people who were confirmed positive counted.
Lesosky said there were other considerations and these varied from country to country and setting to setting.
“Poverty puts people at risk and food insecurity may be a bigger risk to population health than slightly higher numbers of cases – these are incredibly difficult and multifaceted decisions for a national government to make and in truth, the disease is only one part of them.”
Lesosky said South Africa does not have an accurate mortality rate. We don’t know how deadly this virus is because we don’t know how many people have been infected and recovered but were never tested.
There were many unknowns, but countries, particularly their health sectors, still needed to prepare for the inevitable new challenges. And despite this uncertainty, decision-makers must decide what needs to be done.
Something borrowed, something new…
Mathematical modelling was one of the tools used to provide them with estimates of the impact of the disease.
Experts from a wide range of disciplines pool their expertise, resources, and data, to build an initial model.
There were a number of different approaches to modelling and to prediction, but again, things can get a little bit tricky.
Researchers in all kinds of fields of inquiry are frequently warned of the danger of making assumptions, but without some assumptions, where would you start?
A set of mathematical or statistical assumptions provides the basis for the model.
And Lesosky said researchers used their best educated guesses to build the initial model. They may also include data from countries that have already been through the epidemic.
That best guess might yield a model that was totally unreasonable or a fairly reasonable model suited to the local scenario, but needing a few tweaks.
What of the models being used in other countries and how were the researchers using them in South Africa faring up?
Lesosky took a diplomatic line and pointed out that it was still early days.
“Some individuals and groups who have received attention for their predictions may not have had sufficient experience in modelling infectious disease, or they may have made bad assumptions,” she said.
Modelling infectious diseases was an area that needed expertise and required knowledge both about clinical and virological aspects of the disease and the contextual and social aspects of the population being modelled, she said.
“We are still missing a great deal of that context and information because we’ve only known about this virus for about 6 months.”
Things would get better, though.
Initial models would be refined as we continue collating data about the infection rate and the mortality rate. When that happens, the models would supply increasingly useful predictions, appropriate for South Africa.
It’s a complex business, with often long and interlinked chains of cause and effect.
Some of the wilder claims doing the rounds in social and other media overlook the subtleties in pursuit of colorful villains. The truth, though, can be a lot more complicated and less exciting and the models researchers use, unavoidably, are far from exact.
Suliman doesn’t pretend to have the answers and agrees they cannot be viewed in isolation.
But he hopes by presenting the numbers more clearly he can help. This included by adding to the democratic discourse.
The authorities needed to go further in taking the public into its confidence.
“Prof Karim’s presentation was fantastic, but why was it only done once and why aren’t these presented to the nation more regularly? I hope that my daily updates can help somewhat in this regard,” he said.
“It is important in this situation to use statistics in justifying nationwide and provincial decisions and people cannot be asked to simply blindly follow the people in charge,” he said.
“Most of the nation appreciated the early lockdown and decisive action in South Africa and it was explained and justified, but the lockdown extension was difficult to justify without having ramped up the daily testing at that stage. ”
The numbers, perhaps, don’t lie, but they do need a little help. In these anxious times a little clarity could certainly calm fears. – Roving Reporters
- Fatima Khan has a background in laboratory research and education. She is enrolled on Roving Reporters’ environmental journalism training programme and is an associate editor.
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