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Infectious Diseases

Updated 24 July 2020

Covid-19: More cases than UK, Spain, Italy - but SA has lower mortality rate - we asked experts why

South Africa's Covid-19 cases have surged past the UK, Spain and Italy, hard-hit in the early part of the outbreak - but SA's mortality rate is lower. We spoke to experts.

  • Despite an increase in case numbers, South Africa's coronavirus death rate is lower than in other countries.
  • Local experts explain how these numbers are calculated and what they mean.
  • A young population and early adoption of masks could be behind these figures.

As South Africa is experiencing a surge in coronavirus cases, overtaking European hotspots like Italy, Spain and the UK in total case numbers, our cumulative case-fatality rate (CFR) appears to be a lot lower. 

As of 22 July, South Africa has nearly 395 000 confirmed cases, with 5 940 deaths. The UK has had more 45 586 deaths (nearly 297 000 cases) Spain more than 28 426 (more than 267 000 cases) and Italy more than 35 082 (more than 245 000 cases), despite lower case numbers.

While the stats are impacted by targeted testing strategies with an assumed high rate of underdetection, experts have given Health24 a few possible reasons why our mortality rate is lower. 

How the numbers work when comparing countries

An important concept to grasp is to understand the calculation of the CFR, says Professor Taryn Young, head of Stellenbosch University's Epidemiology and Biostatistics.

This looks at the confirmed number of deaths compared with the confirmed number of cases by dividing the number of deaths by the number of confirmed cases.

"How countries define and report Covid-19-related deaths is important," says Young. "There is the definition on the one hand, and on the other how it gets reported. For example, reporting based on death certificate will take longer and may not reflect in the data on the day the person died."

According to the Health System Response Monitor, countries define Covid-19 deaths mainly in one of two ways – a confirmed laboratory test as used in the UK, Italy and Spain, while others like Germany include clinically diagnosed or probable Covid-19 deaths according to the World Health Organisation (WHO) definition:

"A death due to Covid-19 is defined for surveillance purposes as a death resulting from a clinically compatible illness, in a probable or confirmed Covid-19 case, unless there is a clear alternative cause of death that cannot be related to Covid disease (e.g. trauma). There should be no period of complete recovery from Covid-19 between illness and death."

In South Africa, provinces are responsible for counting the deaths, tracked through hospitals that feed data of positive Covid-19 patients to the provincial health department. 

Not a biological constant value

"There may be delays between symptoms onset and deaths which can lead to underestimation of the CFR," adds Young.

The cumulative number of cases, on the other hand, all depends on testing strategy. "If only those with severe disease are tested, then we don’t have the true denominator for calculating the CFR."

The CFR also isn't a biological constant value, says Professor Elize Webb, a senior lecturer of epidemiology at University of Pretoria's School of Health Systems and Public Health.

"Instead, it reflects the severity of disease in a particular context, at a particular time, in a particular population," says Webb.

"This means that the CFR can increase or decrease over time, as the health system response changes, and that it can vary by location and the characteristics of the infected population."

Underreporting

Many in South Africa also remain undiagnosed, which is why the CFR will overestimate the true risk of death and is also affected by lags in reporting. 

Dr Sibongile Walaza from the the National Institute For Communicable Diseases concurs that it all depends on a country's testing strategy, and how widespread tracing is.

"If a country has limited testing capacity and very few people have access to testing, some of the deaths will not be counted as Covid-19 related deaths," says Walaza.

"It is also possible to allocate deaths to Covid-19 even though [the virus] was not the cause of death."

The infection fatality rate (IFR), however, looks at the real numbers of infection, which at this stage is impossible to know due to limited testing and asymptomatic infections. 

"Without better and more standardised criteria for testing and for the recording of deaths, the real mortality rate is thus largely unknown and we will only be able to calculate the IFR after the pandemic is over," adds Webb.

READ | Study puts coronavirus death rate at 1.4% – but expert suggests it may be lower 

Young population

As for why South Africa might be seeing such low numbers, all the experts point to the importance of age.

"The reasons for different mortality rates will be multifactorial and it may take some time to fully understand why – but I think that the main differences are probably due to South Africa's very different age structure and possibly partially due to different distributions of risk factors for mortality," says Professor Maia Lesosky, head of Epidemiology and Biostatistics at the University of Cape Town. 

She also agreed with Young and Webb that the definition of Covid-19 deaths can vary between countries, and have a large impact on the difference perceived in the data.

Compared to these European countries where the average age of the population is in the 40s according to Statista, South Africans are on average around 27 years of age, making it a very young population. 

Only 9.1% of the population is over the age of 60, compared to Italy where 22.8% of the population is over the age of 65. We know that the elderly have a high fatality risk when it comes Covid-19 due to the virus exploiting health vulnerabilities, and younger, generally healthier South Africans catching the virus are less likely to die. 

"The high mortality in the USA, in my opinion, could be more ascribed to community outbreaks, within places such as old-age homes and frail-care facilities," says Webb.

According to Stats SA, the highest proportions of elderly persons aged 60 years and above are found in Eastern Cape (11.4%), Western Cape (10.3%) and Northern Cape (10.0%). 

However, studies have shown that Covid-19 could have lasting damage to health even in positive cases among younger people with mild or no symptoms, therefore we might not even know the true cost of the disease for years to come.

READ | Children could be facing long-term health effects indirectly linked to Covid-19

Early adoption of masks

While founding member and past chair of Infection Control Africa Network Shaheen Mehtar also postulates that the population age plays a factor, she also believes early adoption of mask-wearing plays a role. 

"Those countries that took on universal masking early have a much lower mortality rate than those that did not," says Mehtar, referencing a preprint study published in medRxiv that still needs to be peer-reviewed. 

The researchers analysed factors that might have contributed to higher Covid-19 mortality rates per-capita in some countries compared to others. One of the biggest indicators they found was that countries that instituted mask policies early on in their outbreak had far lower mortality rates.

"In countries with cultural norms or government policies supporting public mask-wearing, per-capita coronavirus mortality increased on average by just 7.2% each week, as compared with 55% each week in remaining countries."

They found that in Asian countries, the public widely adopted mask-wearing before there was even a surge in cases and deaths and before the government started recommending them or implementing policies.

Reports of non-compliance

Webb adds that countries like China and Singapore had already experienced a similar outbreak in the 2003 SARS pandemic and knew better how to handle it. Their populations were also better sensitised to wearing masks, which is a new concept for countries in the West.

"Most countries in Europe and North America failed to embrace masks early in their outbreaks, and only adopted mask policies after signs of health system overload became apparent," say the researchers. 

This could partly be attributed to WHO's late recommendation of using cloth masks, which they only included in their guidelines in June.

South Africa was quick to issue a mask policy before cases surged at the beginning stages of lockdown, with a survey in the study indicating that 85.6% agreed wearing a mask could help prevent infection in April.

With some reports of non-compliance, one could assume that those not wearing a mask – who are also more likely to become infected – could be younger and not see themselves as high-risk for Covid-19, while the smaller percentage of elderly and high-risk groups are more vigilant mask-wearers and less likely to become infected.

This could be why we are seeing higher infection numbers, yet fewer deaths.

READ | Here are the best and worst materials for face masks

Other factors

While the study also pointed out the impact of population age – low mortality countries had on average 8.9% of their population over the age of 60 compared to 18.9% in the high-mortality countries – they also found a few other factors that contributed to Covid-19 mortality.

Colder countries, high levels of obesity, urban density, open international borders and longer duration of outbreak influenced higher mortality rates. 

Richer, more developed countries also had higher rates despite better healthcare. The mean GDP per capita was $9 350 in the low-mortality countries, and $27 380 in the high-mortality countries.

They did not find containment measures, increased testing and contact tracing to be significant indicators of mortality. 

In the warmer climates of South Africa, around 66.86% of the population lives in urban centres, compared to 83.4% in the UK, 80.32% in Spain and 70.44% in Italy, and our borders for traditional travel have been closed since the end of March. 

Stick to regulations

The one outlier, however, may be the obesity factor. We have one of the highest levels of obesity in the world, while in a country like Italy only 19.8% of the population is considered obese. 

It's important to note that the study doesn't account for number of cases, and their findings – which are still being reviewed – could be considered coincidental and limited by the numbers reported by each country.

Whatever might be behind our lower mortality rates, it remains imperative to stick to regulations like wearing a mask and maintaining physical distancing in order to protect the most vulnerable in our communities. 

READ MORE | Obese Covid-19 patients may have to be hospitalised for longer, new research says

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