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ML1 / Explore
What happens when the contact brake lowers transmission?
This MiniLab starts with public health measures. Rules, guidance and campaigns can reduce risky contacts. In the SIR model, their combined effect becomes one lever called mitigation.
R₀ is the basic reproduction number. It describes how many people one infectious person would infect if nothing slowed transmission down. In ML1, R₀ stays fixed as the reference.
Mitigation is the model version of the contact brake. When mitigation gets stronger, effective reproduction falls below R₀. The wave changes and more people can remain untouched.
What can count as a contact brake
- official distancing rules and gathering limits
- school or workplace regulations that reduce close contact
- general administrative orders and local public-health decrees
- mask rules and hygiene protocols in shared indoor spaces
- testing, isolation and stay-at-home guidance after exposure
- public information campaigns and prevention work that change behaviour
Read ML1 as a simple chain. Public health measures reduce risky contacts. The effective pressure falls. The end state changes.
Read the frame, then move the brake
Population, seed infection and horizon define the example. Mitigation is the open intervention.
Population, seed infection and horizon define the frame of the example. R₀ stays fixed in the background.
Mitigation is the open lever. Moving it shows how public health measures become visible in the wave.
Four cards show the effect
One card fixes the reference. One shows the immediate brake effect. Two cards show the horizon state.
R₀
R₀ · Spread factor
Reference without a brake
Basic reproduction without mitigation. This value stays fixed.
Rₑff (t=0)
Rₑff (t=0) · At start
Immediate brake effect
Effective reproduction right after mitigation starts.
S (t=300)
S (t=300) · Susceptible at horizon
Still untouched at the horizon
People still susceptible at the horizon.
R (t=300)
R (t=300) · Recovered at horizon
Moved through the outbreak
People who have passed through the wave by the horizon.
Take-home Message
When the contact brake lowers transmission, effective reproduction drops below the fixed reference R₀. The wave becomes flatter and more people stay untouched.
SIR Model · Wave pattern
S I R
R₀ · Spread factor R₀ · Spread R₀
2.50
Rₑff (t=0) · At start Rₑff (t=0) · Start Rₑff (0)
2.50
S (t=300) · Susceptible at horizon S (t=300) · Horizon S (300)
103
R (t=300) · Recovered at horizon R (t=300) · Horizon R (300)
897