I suppose the first thing that might come to mind is the correlation between obesity and serious disease outcome. "Pooled analysis show individuals with obesity were more at risk for COVID-19, >46% higher for hospitalization. >113% higher for ICU, 48% increase in death... The underlying metabolic and inflammatory factors of individuals with obesity also play a considerable role in the manifestation of severe lung diseases. [0] Given that only about 20% of sub-Saharan Africa is overweight compared to nearly 70% of North America [1], I might consider this one factor.
[0] https://onlinelibrary.wiley.com/doi/pdf/10.1111/obr.13128