665 to 12-million infected: The possible SA coronavirus numbers

In a week, the number of South Africans who have contracted the Covid-19 coronavirus has gone from one to 17 — the number the minister of health announced on Thursday. That seems like a small jump. Statistically, however, it is a big increase.

To understand what this trajectory could mean, the Mail & Guardian Data Desk has run a basic growth rate calculation using two rates — that of the current spread in the country and that of the average rate of infection in the rest of the world (excluding China). The current average infection growth rate is 13% globally — the number of people being infected is growing by 13% each day. So if one person is infected today, 1.13 people in total are infected tomorrow. By day 6, two people could be infected. If 100 people are infected today, 127 in total could be infected tomorrow.

This growth continues until the virus runs out of people to infect because of actions such as quarantining. At that point it reaches what is called an inflection curve and the rate of its spread slows and reverses, which is what seems to be happening in the original epicentre of the outbreak, Wuhan in China. 

If you use the 13% rate for South Africa, from the 17 people who have already tested positive for Covid-19, the probability is that 665 people could be infected in the next 30 days. On average, 12% of those people will end up critically ill and needing to go to hospital, with between 2 and 8% dying.

If you use South Africa’s current growth rate of coronavirus, which is on average 57%, and if this rate continues, 100000 people will be in need of hospital care in less than a month.

A growth in the virus of that scale has not been seen, with global infections now passing 120000. There is agreement, however, that there will be an uptick in the number of infections in South Africa.

Dr Leaza Jernberg, an independent researcher and consultant, said that the trend in the rest of the world is of exponential increase, where the infection rate is doubling in some countries. She had not seen the M&G numbers and was commenting in general.

“The cases are doubling up every six or so days. If that is the case even the best health care system will take strain. What is more concerning is whether we have enough beds, ICU ventilators and oxygen. We might have enough to cope when it is 50 people but will we have enough resources when it is 150 people?” she asked.

According to the data collected by the Health Systems Trust, as of March 2019 there are about 86 516 beds available in public hospitals.

This includes regional, provincial and specialised hospitals across the country. So far, the government has identified 11 hospitals where people should go.

The majority of people infected do recover and the disease tends to affect people with pre-existing medical conditions and those older than 70 the most.

(John McCann/M&G)

China responded with aggressive quarantines at the cost of its economy and kept deaths to about 3000 people. In Italy, the healthcare system is unable to handle the growth, two weeks into the virus spreading there. In Germany, Chancellor Angela Merkel said this week that two-thirds of the population could be infected. 

During its first 10 days with Covid-19, Germany only had 16 cases but by Thursday this was nearly at 2000 cases. The New York Times quoted Merkel saying: “We have to understand that many people will be infected. The consensus among experts is that 60 to 70% of the population will be infected as long as this remains the situation.”

Merkel said her government’s goal is to slow down the spread of the virus, an approach being adopted by other governments, who say the goal is to flatten out the rate of infections, so there aren’t spikes that then overwhelm hospitals.

In South Africa, the government has been at pains to say there is no need for panic. Health experts have similarly been cautious with making predictions about the rate of infection, explaining that the country has a robust public health system for contact tracing and laboratories are well equipped to provide testing and supportive health care.

Professor Maia Lesosky, the head of the Epidemiology and Biostatistics School of Public Health and Family Medicine at the University of Cape Town, says although the infection rate is growing there should be no undue worry.

“Based on what we have seen in other countries, the global increase in confirmed cases, and the fact that testing being carried out by NICD [National Institute for Communicable Diseases], we should expect to see increases in the confirmed case count in South Africa.

“This is not something that should cause undue worry,” she said.

She added that the speed at which cases increase depends on factors both related to the infectiousness of the disease, the mixing of the population as people move, and other factors, such as the case definition and availability of confirmatory testing.

“It is highly likely that we will see a significant increase in cases over the coming weeks, given what we have seen in other settings, and this should be expected,” said Lesosky

South Africa’s rate of growth is currently much lower than that in the worst-affected countries after China.

Iran has 10075 cases, Italy has 12462 and Germany has 1966 cases.

In Iran and Italy, the growth was initially slow, but then appeared to double every day after 100 cases.

In Italy, reports are beginning to emerge of doctors having to prioritise who they treat, leaving older, more vulnerable patients in favour of treating those who are younger and more likely to survive. 

Jernberg added that another concern which has not been addressed by the state yet is what the strategy is when the infection hits areas such as Tembisa, Khayelitsha and other densely populated areas.

“We need to start thinking about what is our threshold and how do you offer triage in areas like Diepsloot? With people waiting in queues for hours at clinics and hospitals how many could be infected?

“How do you ask the poorest of the poor to self-quarantine and wash their hands when there are scarce water resources?” she asked.

Some 21-million people in South Africa do not have access to clean, or regular water.

The M&G asked Dr Lwazi Manzi, the spokesperson for the minister of health, these and other questions and how the state would deal with the spread in such areas, what precautions can be taken for the spread not to reach such areas and how the infection rate would grow.

Manzi said she would show the minister the questions and that right now communication is strictly restricted to media statements, ministerial briefings and direct interviews.

Professor Lucille Bloomberg from the NICD said that it would be very difficult to predict how Covid-19 would spread in the country but basic hygiene measures must be adhered to in all settings.

“There are too many factors that are different from other countries that could impact the spread. There are many variables. But what we can say is that overwhelmingly infections are mild and self-limiting. The severe disease affects people over 70 and those people with underlying medical problems,” she said.

She added that it would be difficult to use other countries’ experiences.

Bloomberg said that measures such as lockdowns would not be easy in our environment because people don’t have jobs and there are child-headed households.

“We know that about 30 to 50% of people could be affected but we don’t know everything about that. Just remember that influenza can be a serious illness.

“We do need to make contingencies to cope with more patients in our challenged health systems. A lot is being done. People are looking at how to ramp up bed availability and such,” she said.

As the M&G reports in the business section, the spread of Covid-19 globally has hit markets hard and is threatening to put the world economy into another recession.

If this happens, with a looming credit ratings downgrade on the cards, the country has few tools at hand to mitigate the economic impact of measures needed to slow the spread of the virus, such as quarantines.

Concern that hospitals won’t be able to cope with Covid-19 

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M&G Data Desk
The Data Desk is the centre for data journalism at Mail & Guardian
Sipho Kings
Sipho Kings is the acting editor-in-chief of the Mail & Guardian

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