To calculation

 

R₀ (R-naught) doesn’t change just because we start with more cases — it’s a constant for that pathogen in that environment.

✍️ Key Takeaways in Simple Form:

• Incidence = new cases over time.
• More original infections = faster rise in incidence.
• But the R₀ stays the same, no matter how many people start out sick.
• You might see a “spike” in cases if you start with more infected people.

Slide Question:

“What do you think would happen to the incidence of chlamydia in our class if there were two original infections instead of 1?”

How about 10?

🧠 Concept Explained Simply:

This is a thought experiment about R₀ (basic reproduction number) and incidence:

• If 1 person infects 2 people → total of 3 infected
• If 2 people infect 4 → total of 6
• If 10 people infect 20 → total of 30

This assumes an R₀ of 2 (each person infects 2 others).

So, more starting infections = faster spread = higher incidence.