Authors of the research, published Friday in the journal BMJ Global Health, predicted a lower infection rate than in other parts of the world like Europe and the US, with fewer severe cases and deaths.
But while they said many African nations had been swift to adopt containment measures, they warned that health systems could still quickly become overwhelmed.
"Our model points to the scale of the problem for health systems if containment measures fail," said the authors.
The study comes amid stark warnings that COVID-19 threatens a health emergency in developing nations where fragile health systems are already struggling with an array of other chronic diseases.
Experts at the World Health Organization's Africa office modelled likely rates of exposure to the virus and infection in the 47 countries under its regional remit, which excludes Djibouti, Egypt, Libya, Morocco, Somalia, Sudan and Tunisia.
Some 231 million people, or 22 percent (with a range of 16 to 26 percent) of the one billion people in the region were expected to be infected in the 12 month period -- most of them showing few or no symptoms.
But an estimated 4.6 million people would need to be admitted to hospital, while 140,000 would have severe COVID-19 infection and 89,000 would be critically ill.