Here’s an interesting article from August of 2021 about the relatively low death rates from COVID in Africa. One of its points is that there is evidence that more people in Africa were exposed to COVID and infected with it, at least at a subclinical or mild level, then the relatively small number of COVID tests done there had indicated. So why the better outcomes in Africa in terms of percentages coming down with serious disease? The difference doesn’t seem to reside in failure to report COVID deaths, either, nor was it Africans’ compliance with stringent government policies to reduce the spread. And the data there is probably mostly prior to the vaccine, so it’s not related to that. Africa has had lower rates than the Western industrialized world from the start.
It seems to be a real difference, in part because of this sort of thing:
Population structure and spatial distribution strongly predict the patterns of SARS-CoV-2 transmission in communities. Analysis of spatial and temporal clustering of populations shows a correlation between density/crowding and viral reproduction number. Africa is the least urbanized global region, with 55% of the continent’s population living in rural areas with wide variations across countries. Modelling shows greater reproduction rates in urban areas, and epidemiological data are skewed towards higher cases in urban areas across all countries
So there was somewhat less transmission in the first place because of the rural population distribution. Age of the population was a factor as well:
The small slice of the African population who are older (only 3% of the African population is 65+) live overwhelmingly at home, often with extended families spanning multiple generations. This alone explains a huge discrepancy in cases, as roughly one third to one half of deaths in wealthy countries, such as the U.S., have resulted from superspreading events in elderly nursing homes and assisted living facilities, providing the rationale for prioritizing the inoculation of these older individuals. While multiple family homes generally have more people in a shared space than the typical single-family homes of Western countries, this slightly increased risk of within-household spread is offset by the significantly decreased risk of large-scale superspreading events in the community, often caused by congregate nursing home settings
South Africa has a higher percentage of people in nursing homes than the rest of Africa does, and its COVID statistics indicate a higher death rate.
Africans also spend far more time outdoors and far less indoors than those in the West, also a factor in reducing COVID spread. When Africans are indoors they tend to be sleeping, but:
Even in the case of sleeping, these homes are often well ventilated with outside air, significantly reducing the chance of viral transmission when compared to tightly enclosed indoor spaces in developed countries. Additionally, higher temperatures and UV light intensity have been shown to predict SARS-CoV-2 spread, although the evidence is inconsistent. Prolonged, year-round outdoor living with direct exposure to UV light in mostly warm and tropical climates could partially explain reduced transmission…
But there was also less mortality in those in Africa who did contract COVID, and therein lies an especially interesting tale:
It is well known that people with pre-existing conditions, such as diabetes, chronic respiratory diseases, obesity, and hypertension have a greatly increased risk of moderate to severe complications from COVID-19 infection. Broadly, these conditions are considerably less prevalent in low income and lower middle income countries (LICs and LMICs) when compared to higher income countries (HICs)…
South Africa, which accounts for nearly 40% of all reported COVID-19 cases and deaths in the continent, reports an exceptionally high burden of NCDs…
…[A] recent cohort study in South Africa suggested that HIV was associated with a doubling of mortality risk of COVID-19. This is potentially significant to consider in explaining why South Africa has a disproportionate COVID-19 burden in the continent, given that it also has the greatest number of people living with HIV/AIDS in the world …
The phenomenon of trained immunity may be tempering the COVID-19 burden in the continent. Here, we focus on four elements underlying this hypothesis: (i) BCG [tuberculosis] vaccinations, (ii) exposure to varied commensal microorganisms, or the “hygiene hypothesis”, (iii) prevalence of infectious diseases, and (iv) historical use of herbal plants and remedies.
The four above categories are all interesting and well worth reading about, but the possibility of exposure to malaria and malaria medication having an effect is of special interest and is treated in section (iii), prevalence of infectious diseases. Here’s an excerpt:
This pathogenic environment [in Africa] precipitates the wide use of antibiotics, antimalarials, and other drugs to treat NTDs, such as azithromycin and ivermectin often distributed through mass drug administrations, which might counteract to mitigate COVID-19 morbidity. In particular, used widely over several decades in SSA, ivermectin has been spotlighted as a potential treatment for COVID-19, including by the NIH. Researchers have postulated that “circulating viruses or parasites in the African subcontinent” could explain high SARS-CoV-2 antibody seropositivity. For instance, of 228 million cases of malaria worldwide in 2018, 93% were in SSA [sub-Saharan Africa]. Notably, South Africa is not generally endemic for malaria and other NTDs. Intense malaria exposure (which is frequent in many rural areas in SSA and much less so in urban areas, and not at all in South Africa or in northern Africa countries) has a strong influence on the immune system and could contribute to a better trained immunity. It is possible that infection by malaria alone may overstimulate the immune system and confer an immune advantage when compared to nonexposed populations. To further investigate this potential role, as very few to no communities outside of Africa are holo-endemic for the disease, mechanistic studies would be needed to determine if there is cross-immunity between malaria and SARS-CoV-2 exposure.
There are also possible genetic factors, including one the article doesn’t mention: a population’s proportion of Neanderthal genes. It first occurred to me that this was a factor while watching a YouTube video on Neanderthals (I no longer recall which video) that mentioned that Neanderthal DNA contains some genes that predispose carriers to a more severe reaction to COVID and a greater likelihood of death from it (also see this).
There are probably a host of factors explaining the African results, not just one or two. The issue highlights the complexity that is often discovered when trying to analyze why COVID vulnerability differs from one population to another.