The most widely accepted factor is Africa’s youthful population. Only about 3 per cent of Africans are over the age of 65, the age group in which illness and death from the coronavirus are most common. (By comparison, about 18 per cent of Canada’s population is over the age of 65.)

Africa’s low COVID-19 death rate has multiple causes, WHO says — https://www.theglobeandmail.com/world/article-africas-low-covid-19-death-rate-has-multiple-causes-who-says/

• Case fatality rate of 2.4
• lower testing rates
• youthful population
• 90% of cases in people <65 years of age
• more rural areas, more time outdoors
• strict lock downs early
• poor road network, limited international flights