Modelling COVID-19 transmission in Africa: countrywise projections of total and severe infections under different lockdown scenarios

Abstract

Objectives: As of 13 January 2021, there have been 3 113 963 confirmed cases of SARS-CoV-2 and 74 619 deaths across the African continent. Despite relatively lower numbers of cases initially, many African countries are now experiencing an exponential increase in case numbers. Estimates of the progression of disease and potential impact of different interventions are needed to inform policymaking decisions. Herein, we model the possible trajectory of SARS-CoV-2 in 52 African countries under different intervention scenarios.

Design: We developed a compartmental model of SARS-CoV-2 transmission to estimate the COVID-19 case burden for all African countries while considering four scenarios: no intervention, moderate lockdown, hard lockdown and hard lockdown with continued restrictions once lockdown is lifted. We further analysed the potential impact of COVID-19 on vulnerable populations affected by HIV/AIDS and tuberculosis (TB).

Results: In the absence of an intervention, the most populous countries had the highest peaks in active projected number of infections with Nigeria having an estimated 645 081 severe infections. The scenario with a hard lockdown and continued post-lockdown interventions to reduce transmission was the most efficacious strategy for delaying the time to the peak and reducing the number of cases. In South Africa, projected peak severe infections increase from 162 977 to 2 03 261, when vulnerable populations with HIV/AIDS and TB are included in the analysis.

Conclusion: The COVID-19 pandemic is rapidly spreading across the African continent. Estimates of the potential impact of interventions and burden of disease are essential for policymakers to make evidence-based decisions on the distribution of limited resources and to balance the economic costs of interventions with the potential for saving lives.

Keywords: epidemiology; public health; respiratory infections.

Figure 1

Modified SEIR model structure. Susceptible individuals, S, become exposed, E, to SARS-CoV-2. A proportion of these individuals become symptomatically infected with severe symptoms, I_S, or non-severe, symptoms, I_N, while the rest become contagious with mild or no symptoms, C. Asymptomatic or mildly symptomatic, moderately symptomatic and severely symptomatic individuals recover, R and severely infected individuals may also die, D.

Figure 2

Projected total infections over time when parameters are normalised for the age distribution of the population in each country. Areas shaded in grey denote lockdown duration. SD, social distancing.

Figure 3

Projected total infections over time when parameters are normalised for the age distribution of the population in each country and the fraction of the under 70-year-old population with HIV/AIDS and or tuberculosis. Areas shaded in grey denote lockdown duration.

Figure 4

Percent change in peak total infections under interventions, compared with baseline, parameters adjusted by age only. Values in parentheses represent the duration of lockdown in the respective countries. Percent change was calculated relative to a baseline scenario of disease spread with no intervention.

Figure 5

Percent change in peak severe infections under moderate lockdown scenario, parameters adjusted by age only. SD, social distancing.