Simulate Daily Disease Spread

Simulation Board

A

B

C

D

E

F

1

2

3

4

5

6

  • Susceptible

    • Susceptible
    • Susceptible
      and Close Contact
    • Susceptible
      and Close Contact (highlighted)

  • Infectious

    • Newly
      Infectious
    • Infectious

  • Removed

    • Newly
      Recovered
    • Recovered
    • Vaccinated

  • Susceptible

    • Susceptible
    • Susceptible
      and Close Contact
    • Susceptible
      and Close Contact (highlighted)

  • Infectious

    • Newly
      Infectious
    • Infectious

  • Removed

    • Newly
      Recovered
    • Recovered
    • Vaccinated

Settings | Day 0

Before you begin the simulation (Day 0), enter numbers between 1 and 100 as the initial Transmission Probability and initial Recovery Probability.

You can change these two probabilities at the beginning of each day in the simulation.

Transmission Probability (%)
In this model, the transmission probability is the probability (0–100%) that a pathogen will spread from an infectious individual to a susceptible close contact on a given day.
  • For example, a transmission probability of 25% means that there is a 25% (1 in 4) chance that a susceptible individual will become infected if they are a close contact of an infectious individual.
  • If the transmission probability is small, it is less likely the pathogen will spread from an infectious individual to a susceptible individual.
  • If the transmission probability is large, it is more likely the pathogen will spread from an infectious individual to a susceptible individual.
Recovery Probability (%)
In this model, the recovery probability is the probability that an infectious individual will recover on a given day. It depends on how long an infection lasts on average.
  • For example, if an infection lasts 5 days on average, there is a 1 in 5 chance that an infectious individual will recover on any given day. So, the recovery probability is 1/5 = 0.2 = 20%.
  • If the recovery probability is small, an infectious individual will remain infectious for a relatively long period of time and has more opportunities to infect others.
  • If the recovery probability is large, an infectious individual will remain infectious for a relatively short period of time and has fewer opportunities to infect others.

Set Initial Case

In this model, the initial case, which is also known as the index case, is the first individual in the population to acquire the disease and become infectious.
  • Select an individual in the population grid as the first infectious case in this population.
  • Select the “Set Initial Case” button that appears.
  • To change the initial case, perform the same action on a different individual.

Simulate each day by following these steps:

  1. For each infectious individual in the population grid, select their icon, then “Simulate New Infections.” Select “Done” when finished with all infectious individuals.
  2. Optionally, select one susceptible individual to vaccinate, then select “Done.” Or select “Skip.”
  3. Reveal the number of recovered individuals by selecting “Simulate New Recoveries.”
  4. Copy the numbers of infectious and removed individuals into the “SIR Data Table,” or turn on “Autofill” to automatically fill in the table. Select “End Day” to proceed.
    :
    Number of Infectious:
    (Newly infectious + infectious)
    Number of Removed:
    (Newly recovered + recovered + vaccinated)

SIR Data Table

Day 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Susceptible 36
Infectious
Removed

SIR Graph

This graph shows changes in the number of individuals in each group (susceptible, infectious, and removed) over time. Listen to the Graph

Finish and Continue to Summary