The Ministerial Advisory Committee on Covid-19 is considering new ways to measure its spread as key questions about how far it has spread continue to plague the government.
The 45-member team of experts from at least 20 universities and international institutions is advising Health Minister Zweli Mkhize on how to manage the spread of virus.
Professor Salim Abdool Karim, who chairs the committee, said in a webinar with News24 on Wednesday information about whether the lockdown had worked would only trickle in this week.
This is because there is a two-week delay between the onset of infection and an infection being reported, so the data regarding infections currently being used by the government is about two weeks old.
“We are working on very limited research on the coronavirus. We need to draw on our experience from other viruses and other diseases,” Karim said.
Screening of possible cases will need to double if experts are to have any hope of understanding the scale of community transmissions, and experts say there are too many variables and unknowns in the Covid-19 case monitoring process to make any definitive findings now.
The government’s strategy includes upscaling its screening, testing and contact tracing programme.
Karim said by 18 April, if the number of people screened reached one million, experts would have a large enough sample size to calculate the rate of community transmissions.
This week, Mkhize confirmed about 460 000 people have been screened so far, adding the screening resulted in around 4 000 tests.
Karim said the one million figure was not informed by any data, necessarily, but it was a good sample size.
This presents a new method for the government on how to measure the outbreak.
Apples and oranges
Karim said he had proposed a threshold of one in 1 000 positive cases would require an extension of the lockdown, but he emphasised there were many considerations being taken into account by the government in its approach to the lockdown, including social concerns and economic strategy.
By 18 April, enough time would also have elapsed since the start of the lockdown to calculate how effective it has been.
But a key issue Karim and the committee was grappling with, was differentiating between “passive and active cases”.
Passive cases refer to those detected in the course of the disease spread, in other words people who showed symptoms and presented themselves for testing.
Passive cases are now being identified as screening and testing is upscaled, presenting a challenge in gaining an understanding on community transmission.
Karim said it would require separating the active and passive cases – “apples from oranges” – to make scientifically supported calculations.
The “key epidemiological question”, said retired mathematician Professor Brian Williams, was whether people who were infected and asymptomatic were also infectious.
Williams, who worked for the World Health Organisation’s (WHO) TB programme for a decade and is now based in Switzerland, added there was a danger there would be many young people, who do not show symptoms but were infected, who would spread the virus to the older population.
It was therefore essential to know whether these people were also capable of also spreading the virus, he said.
An actuarial scientist, who asked to remain anonymous as he is not authorised to speak with the media, said there were concerns over the criteria used to measure Covid-19 cases.
He added data published on an ongoing basis could be misleading as many people did not understand what it meant: not only did the data only reflect numbers of infections from days prior to positive results, but it also did not reflect the absolute numbers of deaths.
For example, he said those who were not tested for Covid-19 prior to their deaths were not included in the figures.
New York revised its death toll this week to include about 3 000 cases that had not been identified as Covid-19 cases prior to their deaths.
Meanwhile, US President Donald Trump was roundly condemned on Wednesday for announcing that the US would freeze payments to the WHO, The Guardian reported.
Trump reportedly said funding would be frozen for 60 to 90 days pending a review of the WHO’s warnings about Covid-19.
The WHO did not immediately respond to a request for clarity on Wednesday about whether this has implications for South Africa.
In South Africa, concerns about outbreaks in medical facilities continues to rise. Twelve staff members, including seven healthcare workers, tested positive at Mediclinic Morningside in Johannesburg.
Netcare Kingsway Hospital in Amanzimtoti, KwaZulu-Natal, has been temporarily closed after an outbreak which was traced to a patient who presented stroke symptoms.