Abstract
The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has expanded into a global pandemic, with more than 220 million affected persons and almost 4.6 million deaths by 8 September 2021. In particular, Europe and the Americas have been heavily affected by high infection and death rates. In contrast, much lower infection rates and mortality have been reported generally in Africa, particularly in the sub-Saharan region (with the exception of the Southern Africa region). There are different hypotheses for this African paradox, including less testing, the young age of the population, genetic disposition, and behavioral and epidemiological factors. In the present review, we address different immunological factors and their correlation with genetic factors, pre-existing immune status, and differences in cytokine induction patterns. We also focus on epidemiological factors, such as specific medication coverage, helminth distribution, and malaria endemics in the sub-Saharan region. An analysis combining different factors is presented that highlights the central role of the NF-κB signaling pathway in the African paradox. Importantly, insights into the interplay of different factors with the underlying immune pathological mechanisms for COVID-19 can provide a better understanding of the disease and the development of new targets for more efficient treatment strategies.
Highlights
The novel coronavirus SARS-CoV-2 was first reported in Wuhan, China, at the end of 2019 and has developed into the most serious global pandemic since the Spanish flu of 1918–1920, with more than 220 million affected persons and 4.6 million deaths worldwide by 8 September 2021 and 6-digit infection rates daily.When looking at the geographical pattern, North and South America and Europe have been affected most by COVID-19, with 85 mio infections (2.1 mio deaths) and 66 mio infections (1.3 mio deaths), respectively, as of 8th September 2021
While the incidence rate may be significantly under-represented by the low testing coverage on the continent, the mortality rate seems to be much lower in Africa compared to other parts of the world, and no excess mortality due to COVID-19 has been reported from African countries (Figure 2f)
We address immunological mechanisms and their correlation with specifics of Africa’s population, genetic factors, pre-existing immune status, racial differences in cytokine induction patterns, high helminth infection rates in tropical regions, and specific factors related to malaria endemic to the sub-Saharan area, such as differences in Duffy antigen expression (DARC, Duffy antigen receptor of chemokines) and continentspecific coverage of various medications related to helminth infection and malaria
Summary
The novel coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) was first reported in Wuhan, China, at the end of 2019 and has developed into the most serious global pandemic since the Spanish flu of 1918–1920, with more than 220 million affected persons and 4.6 million deaths worldwide by 8 September 2021 and 6-digit infection rates daily. Even though the number of new infections has been recently reported to increase, the total numbers are still low on the African continent compared to other parts of the world and are concentrated within a few countries located in Southern Africa, with this particular area accounting for more than 70% of new cases on the continent (Figure 2c,d, WHO weekly epidemiological update, Edition 50, 27 July 2021 [1]). While the incidence rate may be significantly under-represented by the low testing coverage on the continent, the mortality rate seems to be much lower in Africa compared to other parts of the world (see chapters below), and no excess mortality due to COVID-19 has been reported from African countries (Figure 2f) This is in sharp contrast to what had been expected considering Africa’s generally fragile health system, infrastructure, limited availability of trained medical personnel, and limited access to medical supplies and equipment [3,4].
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