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Age, genes, data or prevention … why does Africa have fewer deaths from covid-19?

When the threat of a COVID-19 pandemic emerged earlier this year, many feared its effects in Africa. Concerns about the combination of overburdened and underfunded health systems, and the already existing burden of infectious and non-infectious diseases, led to frequent will talk about it in apocalyptic terms.

However, that has not been the result. On September 29, the global death toll exceeded the million (the actual figure will, of course, be higher). That same day, count of fatalities in Africa yielded a cumulative total of 35,954.

Africa It represents 17% of the world’s population, but only 3.5% of reported COVID-19 deaths. All deaths are significant, we shouldn’t discount seemingly low numbers and the data collected is of variable quality, but the gap between predictions and what has actually happened so far is staggering. There has been a lot of discussion about why this gap is due.

As leaders of the covid-19 team of the African Academy of Sciences, we have followed the development of events and presented various explanations. In many African countries, transmission has been high, but severity and mortality have been much lower than the original predictions, based on the experience of China and Europe.

We argue that Africa’s much younger population explains a large part of the apparent difference. The remaining part is probably due to the lack of reliable data on what happens, although there are other plausible explanations: climatic differences, pre-existing immunity, genetic factors or behavioral differences.

Given the enormous variability of conditions across the 55-state continent, the exact contribution of any of the factors is likely to change from country to country. But the bottom line is that what initially seemed like a mystery is now less puzzling as more scientific evidence emerges.

The importance of age

The most obvious influencing factor in low mortality rates is the age structure of the population. In many countries, the risk of death from covid-19 for people 80 years and older is approximately one hundred times higher than for people in their 20s.

This is best appreciated with an example: as of September 30, UK had counted 41,980 deaths from covid-19, while Kenya had counted 691. The population of the United Kingdom is about 66 million people, with an average age of 40 years. Kenya’s population is 51 million and the median age is 20.

Taking into account the size of the population, the number of deaths in Kenya would have been estimated at about 32,000. However, if it were also corrected for population structure (assuming UK age-specific deaths apply to the Kenyan population structure), they would wait around 5,000 deaths. There is still a big difference between 700 and 5,000. How can it be explained?

Other possible factors

One possibility is the lack of identification and registration of deaths.

At the beginning of the pandemic, Kenya, as many countries, had little capacity to conduct tests, and the specific registration of deaths is complex. However, Kenya quickly developed their ability to do analysis and the specific attention paid to the search for deaths makes it unlikely that a difference of this magnitude can be fully explained with the missing information. Explanations based on other factors have not been lacking.

High temperatures and humidity

A study A recent one in Europe reported significant declines in mortality due to higher temperatures and humidity. The authors proposed that this phenomenon could be due to the fact that the mechanisms by which our airways clear the virus work better in warmer and more humid conditions. This means that people may be getting fewer virus particles in their bodies.

It should be noted, however, that a systematic review of global data, although it confirmed that hot and humid climates seem to reduce the spread of covid-19, it also indicated that these variables alone cannot explain the great variability in the transmission of the disease. It is important to remember that there is considerable climatic variation on the African continent. Not all climates are hot and humid, and even if they were, they may not be constant throughout the year.

Other hypotheses include the possibility of pre-existing immune responses due to previous exposure to other pathogens or to BCG vaccination, a tuberculosis vaccine given at birth in most African countries. An extensive analysis – involving 55 countries, representing 63% of the world’s population – showed significant correlations between increased BCG vaccine coverage at an early age and better outcomes from COVID-19.

Genetic factors may also be relevant. A haplotype (group of genes) recently described, associated with an increased risk of severity and present in 30% of genomes in South Asia and in 8% of Europeans, it is almost absent in Africa.

The role of this and other factors (such as potential differences between social structures or mobility) are the subject of ongoing research.

A more effective response

Another important possibility is that the public health system response On the part of African countries, prepared by previous experiences (such as outbreaks or epidemics), it was simply more effective than in other parts of the world in controlling transmission.

However, in Kenya it is estimated that the epidemic reached its peak in July, with around 40% of the population in urban areas infected. A similar picture is emerging in other countries. This implies that the measures put in place had minimal results in viral transmission, although it raises the possibility that group immunity now plays an important role in limiting transmission.

In addition, there is another important possibility: the idea that viral load (the number of particles transmitted to a person) is a key determinant in gravity. It has been suggested that masks reduce viral load and that their widespread use can limit the chances of developing a serious illness. Although the WHO recommends wearing masks, their compliance is uneven and lower in many European countries compared to many parts of Africa.

So is Africa free of suspicion? Obviously not. There is still a lot of virus left and we do not know what can happen as the interaction between the virus and people advances.

Still, one thing is clear: the after-effects of the pandemic will be a real challenge for Africa. We refer to the severe interruptions of economic and social activities, and the potentially devastating effects of the reduction of care services that protect millions of people, such as routine vaccinations and malaria, tuberculosis and HIV control programs.

Research agendas

Among the main implications of the new landscape is the need to re-evaluate African research agendas related to COVID-19. While many of the originally identified priorities remain, it is likely that their relative importance has changed. The key is to deal with problems as they are now and not as they were imagined six months ago.

The same is true of public health policies. Of course, basic measures such as hand washing are still essential (regardless of covid-19) and masks should continue to be used while there are high levels of transmission of the coronavirus. However, other measures with broader effects, especially restrictions on educational or economic activities, must continue to be monitored.

The key now is to increase vigilance and ensure that responses are flexible and based on quality data in real time.

Kevin Mars is senior advisor and co-leader of the covid-19 team of the African Academy of Sciences. He is also Professor of Tropical Medicine and Director of the Oxford Initiative for Africa at the University of Oxford. Moses Alobo He is the director of the African Academy of Sciences’ Grand Challenges Africa program and co-leads the covid-19 initiative. Become part of the Tutu Fellowship.

This article was originally published on The Conversation Translated, with the collaboration of Africa House, by Elvira González-Sosa Suárez. See here the edition of The Conversation Spain.

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