OBWOGO: To Explain the “Low” Covid-19 Death Rates in Africa, Stop Counting the Body Bags & Follow the Science Instead (Part 13: Think-Like-A-Virus

I recently read a story published in Science, a non-profit publication, pondering the question of why the Covid-19 pandemic seems to have spared Africa so far.

Here’s the jigsaw puzzle: Africa recently reported its millionth official COVID-19 case with fewer than one confirmed case for every thousand people and just 23,000 deaths so far. Yet, if you look at the antibody surveys done so far, more Africans have been infected with the coronavirus, creating a huge disparity between antibody data and official case and death counts, the report said. 

I’ll delve into what I think is going on in a while but, oh boy, this is exhausting. Cynics have seized on these findings to argue that the emphasis currently put on preventing SARS-CoV-2 in Africa is misplaced.

Look, when the virus first erupted in Dec. 2019 in Wuhan, China, the rest of the world was watching with a sense of schadenfreude. When it reached the West, Italy became the epicenter and pariah state. President Trump was quoted on March17, “You look at what’s going on with Italy. We don’t want to be in a position like that.” He continued to dismiss the “Chinese virus” as a mild flu even as the first cases were reported in America.

Fast forward to a few months, and the United States with barely four per cent of the world’s population accounted for 25 per cent of the coronavirus cases, at some point, and had a fatality rate five times higher than the global average.

If you’ve never had a nightmare where you’re running away from a monster and, no matter what you throw, it keeps lurching on, this is real: In Tanzania, President John Magufuli declared sometime in August that his country was virus-free after banning testing and promoting an unproven herbal tea from Madagascar as a cure. He’s discouraged social distancing and wearing of masks and invoked the power of prayers.

So, what could explain the apparent low death-to-infection ratio? A straight answer is that I’ve no idea at all. But then, the good news is that we now know enough about how SARS-CoV-2 that causes Covid-19 is transmitted to hazard some intelligent guesses.

A good place to start is by comparing test rates for SARS-CoV-2 active infections.

It’s a fact that testing in many African countries is too low to make the data any meaningful. The World 'Human' Organisation (WHO) recommends one test per 1,000 people per week. Some independent reports show that most countries in Africa undertook fewer than 8,000 tests per million people. For example, among the lowest testing rates are Tanzania, DRC, Niger, Chad, and Burundi at 63, 467, 373, 383, and 563 tests per million. 

Please, don’t tell anyone this: Nigeria, the continent’s most populous nation, tests one out of every 50,000 people per day.

To compare, Britain, United Arab Emirates and Singapore have conducted 205,782, 472,590, and 199,904 tests per million respectively.

In fact, experts have warned that without international support to increase testing, many African nations could face “an undetected and uncontrolled spread” akin to driving a car with the lights off in the dark.

Related to test-rates is the type of tests used and their efficacy. There are three different types of tests: Molecular tests (also called PCR), antigen tests (test for active infection like PCR but used for surveillance) and antibody tests (can't tell if you've active infection).

First, we know that the accuracy of antibody tests varies widely and these tests cannot be relied on except for these specified purposes. But being inaccurate is not the only problem with antibody tests. Some experts have argued that because antibody tests can’t tell if you’re immune to subsequent infections, they’re useless in deciding whether to ease mask wearing or social distancing.

Even the most widely used and accurate test, the PCR, may be apt for clinical diagnosis but it’s not very useful for public health and policy-decision making. The truth is that as currently used, PCR tests are more qualitative (give a yes or no answer— infected or not infected) than quantitative (amount of virus in the body and contagiousness).

So, how does PCR testing work? By amplifying the viral genetic matter in cycles. Now assume that two PCR machines or laboratories have set their cycle thresholds, or CTs— the number of amplification cycles needed to find the virus— limits at 37 (Lab A) and at 40 (Lab B). What this means is that if my viral load is comparatively low, I could test positive to SARS-CoV-2 with machine B and negative with A.

Let’s forget CTs for now and consider a more burning question: Even if the tests are few and inaccurate, surely, we can’t miss the body bags, can we? I’ll start with the obvious.

First, Africa has a more youthful population and lower rates of obesity compared to many countries in the west. But then, as more young people test positive for coronavirus, there’s no guarantee that more of them won’t die as multiple risk factors coalesce.

Second, we now know that airborne transmission is a far greater risk than contaminated surfaces and that the virus spreads through singing and shouting as much as through coughing. What that means is that while any infected person is a potential vector, it’s the superspreading events—in bars, schools, churches, weddings, funerals and such crowded places— that are major drivers of the pandemic. It’s estimated that just 10 to 20 per cent of coronavirus infections account for 80 per cent of transmissions and most people who get infected simply don’t pass it on.

Third, when it comes to transmission, a positive test is meaningless without considering the amount of virus one is exposed to. As I’d mentioned, the CTs depend on the patient’s viral load and because these are rarely included in the results sent to the doctor, a positive test doesn’t indicate how infectious someone is. In one survey in Massachusetts, 90 per cent of people testing positive carried barely any virus that could be deemed contagious.

Fourth, researchers have tentatively estimated that about 40 per cent of coronavirus infections do not produce any symptoms and when people wear masks, the proportion of asymptomatic cases increases. Scientists have concluded that although face covering do not make people impervious to infection, they could lead to milder disease, potentially reducing hospitalisations and deaths.

Lastly, it’s possible that weak mortality surveillance systems (Covid-19 mortality rates are based on measuring the number of excess natural deaths reported) could be obscuring the true picture.

Ultimately, the jury is still out and I'd urge caution for now.

Dr Obwogo is a medical doctor, specialist in Public Health Medicine, author, entrepreneur, consultant, past Chevening scholar and founder of Kienyeji Kenya Farmers’ Network Initiative (KiFaNi).

Email: [email protected]

Website: www.KienyejiKenya.com