When the threat of a Covid-19 pandemic emerged earlier in the year, many feared its effects in Africa . Concern about the combination of overburdened and underfunded health systems, and the already existing burden of infectious and non-infectious diseases, have often been talked about in apocalyptic terms.
However, that has not been the result . On September 29, the global death toll surpassed one million (the true figure will, of course, be higher). That same day, the death toll in Africa came to a cumulative total of 35,954.
Africa accounts for 17% of the world’s population, but only 3.5% of reported COVID-19 deaths .
All deaths are significant, we should not discount seemingly low numbers and the data collected is of variable quality, but the gap between the 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 the 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 a mystery is now less puzzling as more scientific evidence emerges.
The most obvious factor influencing the low mortality rates is the age structure of the population. In many countries, the risk of death from COVID-19 for people 80 years of age and older is about 100 times higher than for people in their 20s.
This is best appreciated with an example: as of September 30, the UK had accounted for 41,980 COVID-19 deaths, while Kenya had accounted for 691. The UK population is around 66 million people, with an average age 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 around 32,000.
However, if it were also corrected for population structure (assuming UK age-specific deaths apply to Kenya’s population structure), around 5,000 deaths would be expected. There is still a big difference between 700 and 5000. How can this be explained?
At the beginning of the pandemic, Kenya, like many countries, had little testing capacity, and the specific recording of deaths is complex.
However, Kenya quickly developed its analytical skills, and the specific attention paid to finding deaths makes it unlikely that a difference of this magnitude can be fully explained by the missing information. Explanations based on other factors have not been lacking.
A recent study in Europe reported significant declines in mortality due to higher temperatures and humidity. The authors proposed that this phenomenon could be because 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, while confirming that hot and humid climates appear to reduce the spread of COVID-19, also indicated that these variables alone cannot explain the great variability in transmission of COVID-19. the illness.
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. A comprehensive 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 COVID-19 outcomes.
Genetic factors may also be relevant . A recently described haplotype (group of genes) associated with an increased risk of severity and present in 30% of genomes in South Asia and in 8% of Europeans, is almost absent in Africa.
The role of this and other factors (such as potential differences between social structures or mobility) are subject to ongoing research.
Another important possibility is that the response of the public health system by African countries, prepared by previous experiences (such as outbreaks or epidemics), 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 implemented 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 of severity . Masks have been suggested to lower viral load and that their widespread use may limit the chances of developing serious illness. While 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 disease control programs. HIV.
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, their relative importance has likely changed. The key is to deal with problems as they are now and not as they were imagined six months ago.
The same goes for 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 coronavirus transmission. 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
