COVID-19’s ‘Slow Burn’ – Africa’s Low Death Rate Puzzles Researchers
Minister Jackson Mthembu assesses government’s response to COVID-19 at Harry Gwala District Municipality, South Africa 5 September 2020

Cape Town, South Africa – Dire predictions of Africa being overwhelmed by a tsunami of COVID-19 infections and deaths have not materialized – yet – and this is confounding many researchers.

So whether the reason is the continent’s youthful population,  a certain level of  “herd immunity” gained from prior exposure to other coronaviruses, or simply a lack of adequate disease surveillance, experts are trying to understand the reasons why.

In early August, when the continent recorded one million COVID-19 cases  Dr Matshidiso Moeti, the World Health Organization’s regional director for Africa, described the pandemic as a “slow burn” – and that still seems to be the case as the world marks a full six months since the global health emergency was declared to be a “pandemic” by WHO.

Officially, Africa accounts for a mere 4% of the world’s cases and 3% of deaths, according to the latest statistics from the World Health Organization (WHO).  In contrast, Africa represents some 17% of the world’s population.

As encouraging, the rate of new infections has slowed in the continent’s worst affected countries, including South Africa and Egypt.

But on a more sober note, the pandemic is gaining momentum in some countries, notably Congo Brazzaville, Burundi, Central African Republic, Mali, Angola, Cameroon and South Sudan.

Warning Against Complacency

Scientists have warned against complacency, saying that a second wave is possible and that the continent’s health services could still easily be overwhelmed by COVID-19.

The total number of deaths reported in 45 countries of the region was 22 150 as of the first week of September, for an overall case fatality rate (CFR) of 2.1% – which is half the global average and way lower than the UK (11.7%) and Italy (12,7%).

But two important studies point to Africa’s infection rate being much higher than the official figures.

In the first study, researchers tested the blood samples of Kenyan blood donors between the end of April and mid-May and found that 5.6% had SARS-CoV-2 antibodies. Almost 10% of donors in the popular tourist of Mombasa, Kenya were positive. Yet  at the time, Kenya’s official infection rate was only 2093 cases and 71 deaths.

“This contrasts, by several orders of magnitude, with the numbers of cases and deaths reported in parts of Europe and America when seroprevalence was similar,” concluded the Kenyan researchers.

South Africa – More COVID infections and deaths than officially reported – but mortality still below European levels?
Total cases and coronavirus deaths on 14 Sept 2020. Numbers change rapidly

Last week, South African researchers told a media briefing that a whopping 40% of the pregnant women, as well as people with HIV, who visited Cape Town’s public health facilities had SARS-CoV-2 antibodies.

The samples were collected during the country’s pandemic peak in late July and early August from 2 700 people who had no symptoms and were simply at facilities for routine care, according to Professor Mary-Ann Davies, director of the University of Cape Town’s Centre for Infectious Disease Epidemiology and Research.

Meanwhile, the South Africa Medical Research Council, which conducts robust surveillance into mortality trends,  recorded 41,424 “excess deaths” between 6 May and 25 August in comparison to last year.

If the evidence of much higher infection rates is combined with these “excess deaths”, then South Africa’s pandemic trajectory is in line with global trends, according to Professor Andrew Boulle, a public health specialist with the Western Cape health department.

“Crudely, African and other poorer countries ought to have seen about a quarter of the mortality of Europe, given the same incidence and age-specific infection fatality ratios because of the much younger populations,” says Boulle, who is also public health medicine professor at the University of Cape Town.

Serology from overcrowded slums in South Africa and India shows that “seroprevalence is much, much higher than in Europe and North America,” says Boulle. This indicates that South Africa’s hospital cases the mere tip of the infection iceberg.

“I have seen some articles questioning why Africa was not harder hit but, to be honest, I think lower morbidity and mortality was entirely predictable,” he added.

In African countries with less rigorous mortality data, the true extent of COVID-19 deaths may never be known. There is anecdotal evidence that hospitals are filling up in Uganda, as well as reports of delays in tests and poor hospital infection control practices in a country that was once praised as a model for COVID containment.  Meanwhile, funerals have increased in places like Somalia.  Even so,  given the global research community’s scrutiny and measures put into place to track diseases such as cholera, measles and Ebola,  it is unlikely that African countries would be able to conceal abnormally high deaths over a long period of time.

South African Researchers Explore Possible Protective Factors: Youth, Prior Exposure to other Coronaviruses, Vaccine History
The relative youth of Africa’s population may be one reason why coronavirus death rates are lower across the continent.

So how is Africa keeping its hospital cases and deaths lower than predicted? There are a few popular theories.

The first is the relative youth of Africans. Around 60% of Africa’s population is under the age of 25 and only 3% of people living in sub-Saharan Africa are over the age of 65. In contrast, over 20% of the Italian and French populations are over this age and this is where the biggest deaths have occurred globally.

While there are likely to be many more cases than recorded, a high proportion of people infected would have few symptoms and could recover without treatment, simply because of their age.

The second is that some regions or communities already may have developed some kind of “herd immunity” thanks to earlier exposure to other coronaviruses that manifest, such as  the common cold.

Professor Shabir Madhi, head of vaccinology at the University of the Witwatersrand, posited this idea at a symposium hosted by his university and Columbia University last Friday:

Referring to the Cape Town study where 40% of people were seropositive, Madhi said that “there was a huge infection rate in urban areas and quarter of those who tested positive for virus were completely asymptomatic”.

“One of the factors for why so many people are asymptomatic is that here may be some herd immunity underpinning the response, possibly as a result of people being exposed to other common cold coronaviruses over two or three years, ” said Madhi.

Professor Marc Mendelson is head of infectious diseases at the University of Cape Town, and oversees the COVID-19 response at Groote Schuur Hospital, which was at the epicentre of South Africa’s pandemic about six weeks back.

He says that the country’s true infections are “probably somewhere in the region  of six to 15 million”.

“Why South Africa was better off than expected is still in the realms of hypothesis,” adds Mendelson. “I think it is a combination of factors. My top three most likely factors are cross-immunity relating to pre-existing infections with humbler coronaviruses; younger age of the population meaning that less mortality and more asymptomatic or pauci-symptomatic cases, (most of which would have been undocumented); and high transmission rates in high density areas, which drove herd immunity, while compliance with social distancing, masks, and hand hygiene reduced transmission in low density areas”.

He added that these factors may apply to other African countries, but there were also “a number of unknowns” including a lack of testing and laboratory capability.

Professor Helen Rees, who is chair of the WHO Africa Regional Immunisation Technical Advisory Group, said researchers were also examining whether the childhood vaccinations for measles, mumps and rubella (MMR) and tuberculosis – the BCG (bacillus Calmette-Guérin) jab  – offered any protection.

Prevention Policies May Be Keeping Death Rates Low – But ‘Slow Burn’ Still a Threat
South African peacekeepers are distributing awareness-raising pamphlets in a school in North Kivu, Democratic Republic of the Congo

Scott Dowell, an infectious diseases specialist at the Bill and Melinda Gates Foundation, believes that there are “several reasons for why the impact is so low in Africa”.

“The first is that African leaders identified COVID-19 early and their response was robust and quick,” Dowell told the Columbia-Wits symposium. “Then there is age. Very few Africans are over the age of 65 relative to other parts of the world. Over 50% of Africans are between the ages of five and 25 and at low risk of mortality.”

However, Dowell’s final reason was “the 50-fold lower rate of testing” on the continent due to lack of tests and restrictions on who can get tested – meaning that many more cases of infection, and by implication deaths, are really being caught and tracked.

A briefing note by  Resolve to Save Lives, the initiative led by former US CDC director Tom Frieden, concludes that, “a younger age distribution, lower overall population density, warmer temperature, less urbanization and other factors common in Africa tend to favor less transmission and less severe disease.”

But Resolve continues: “Conversely, larger households, high rates of malnutrition, high rates of infectious diseases and other factors may lead to additional burden in comparison to other regions. The balance of these factors will drive trends in the number of people who become sick and the number who die, regardless of whether disease surveillance is optimal.”

Boulle says that, given higher death rates from other illnesses – tuberculosis and HIV in South Africa – “it is possible that the mortality experience due to COVID-19 is less noteworthy and probably largely undocumented.”

However, while the “slow burn” development of the pandemic might be less immediately devastating, it will require sustained resources over a longer period of time and there is a high risk of health-worker fatigue.

Image Credits: Government ZA, WHO, Grassroots Soccer/Karin Schermbrucker , MONUSCO/Force.

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