Age could be driving variable SARS-CoV-2 epidemic trajectories worldwide

Area of Science:

• Epidemiology
• Mathematical Modeling
• Public Health

Background:

• Geographic spread of SARS-CoV-2 infections is heterogeneous.
• The role of age in SARS-CoV-2 transmission, severity, and mortality requires further investigation.

Purpose of the Study:

• To explore how age distribution influences SARS-CoV-2 epidemic trajectories.
• To analyze age-driven differentials in infection spread, epidemic potential, and disease severity across countries.

Main Methods:

• An age-stratified deterministic mathematical model was employed.
• The model was applied to 159 countries and territories with populations ≥1 million.
• A worst-case pandemic scenario was assumed for analysis.

Main Results:

• Significant regional differences in epidemic trajectories were observed, linked to population age distribution.
• Countries with older populations (e.g., Europe) showed higher median R0 (2.05) and cumulative infection incidence (69.0/100 persons) compared to younger populations (e.g., Africa; R0: 1.05, incidence: 22.5/100 persons).
• Higher rates of severe/critical disease (13.0/100) and death (3.9/100) were projected in regions with older populations.

Conclusions:

• Population age structure is a key driver of variable SARS-CoV-2 epidemic trajectories globally.
• Countries with predominantly adult/elderly populations may face larger, faster epidemics without interventions.
• Despite age-related differences, the pandemic poses a significant threat worldwide, necessitating continued vigilance and interventions.