Why South Africa’s coronavirus numbers look so strange

South Africa’s COVID-19 coronavirus epidemic does not follow the same trajectory as any other country in the world. This is according to Salim Abdool Karim, who chairs the Minister of Health’s COVID-19 advisory committee.

In nearly every country where the virus has broken out, there was an initial surge in infections. This is generally followed by a series of extreme interventions from the government, resulting in the “flattening of the curve”.

However, the coronavirus epidemic curve in South Africa made a sharp “knuckle” on 27 March 2020 and plateaued.

To illustrate how South Africa’s curve deviates from the rest of the world, Karim showed graphs comparing it to countries like the United States, Spain, Italy, China, and the United Kingdom.

He also showed how South Africa’s curve differs from countries who responded more effectively to the virus, such as South Korea, Japan, and Singapore.

Expected vs actual trajectory

Based on other countries’ experiences with the coronavirus, it was expected that the number of cases in South Africa would be much higher by now.

The Minister of Health for South Africa, Zweli Mkhize, told journalists at the start of April that they expected the total number of confirmed cases to have reached between 4,000 and 5,000 by around 2 April.

Karim has given further context for the Minister’s statement, explaining that South Africa’s epidemic trajectory closely followed that of the United Kingdom.

The chart below compares the epidemic trajectories of South Africa with the United Kingdom from the day each country reported its 100th case of the coronavirus.

Why is South Africa different?

Karim said that there are three possible reasons the epidemic trajectory in South Africa is different:

  1. We are testing less, or just not testing enough.
  2. We are testing enough, but not in the right places. If tests are mainly being done in the private sector, we may not be getting a sense of what the epidemic is doing in poorer communities that don’t have medical aid.
  3. The reduction in the rate the epidemic is growing in South Africa is genuine due to the interventions that were implemented.

According to Karim, the first two explanations are the least likely.

Coronavirus testing in South Africa has remained fairly constant since 23 March, yet the number of people testing positive every day still took a sharp turn.

Karim added that on the day that South Africa’s epidemic plateaued, coronavirus testing by the National Health Laboratory Service increased sharply. This means that public sector testing has increased and we have a reasonable view of what is happening with the epidemic in poorer communities.

This leaves only the third option — something has caused the rate of new infections in South Africa to reduce significantly.

You have to think back two weeks at a time

Karim explained that to understand the coronavirus case numbers you are seeing today, you have to look back at what was happening in South Africa two weeks ago. This is because when someone tests positive for the coronavirus, it reflects an infection from two weeks ago.

“From the time you get infected, you have a period in which you are in incubation that takes about 7 to 10 days,” said Karim.

Patients only start experiencing symptoms after the incubation period, at which point they go to a doctor, clinic, or hospital.

From there the patient needs to receive a laboratory test, and only if the results come back positive is the patient considered an active coronavirus case.

State of disaster interventions worked – Karim

This means that the reduction in the rate of new cases we have been seeing in South Africa these past two weeks may very well be explained by the urgent and drastic interventions implemented as part of the national state of disaster, Karim stated.

Among the restrictions imposed when the national state of disaster was declared on 15 March were:

  • International travel bans from high-risk countries including Italy, Iran, South Korea, China, Spain, Germany, the UK, and the US.
  • Screening and request for self-isolation of South Africans returning home from high-risk countries.
  • Ban on large gatherings, including government events.
  • Schools closed from 18 March.
  • The closure of 35 land ports.

Because of the two-week average incubation period of the coronavirus, the new cases reported in this week will be the first indication of the impact of the lockdown.

Active screening for coronavirus in vulnerable communities

Karim explained that in addition to the regular testing for the coronavirus when patients start feeling sick and go to their doctor, clinic, or hospital, South Africa is also actively screening for the virus among those who are most vulnerable.

There are currently over 28,000 workers actively screening whether people are possibly infected.

Where the screening procedure finds that someone potentially has the coronavirus, they are referred to a lab or clinic for a full test.

As a result of the active screening and the timing of lab results, we should expect large daily variations in the number of new coronavirus cases in South Africa, Karim stated.

“You will see some large numbers and some small numbers… don’t let that bother you,” he said.

Karim said that to decide whether the lockdown must be extended they will be looking at whole weeks’ worth of data at a time.

“We compare weeks with weeks, so that we’re comparing apples with apples.”

Now read: What needs to happen before the coronavirus lockdown is relaxed in South Africa

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Why South Africa’s coronavirus numbers look so strange