Expected secondary cases from one primary case in a fully susceptible population. Outbreak grows if R₀ > 1; herd immunity threshold = 1 – 1/R₀. Measles R₀ ≈ 12–18, SARS-CoV-2 ancestral ≈ 2–3.
Expected secondary cases from one primary case in a fully susceptible population. Outbreak grows if R₀ > 1; herd immunity threshold = 1 – 1/R₀. Measles R₀ ≈ 12–18, SARS-CoV-2 ancestral ≈ 2–3.