Epidemic Contact Graph
Run the Epidemic Contact Graph MicroSim Fullscreen
About This MicroSim
This MicroSim simulates the spread of an infectious disease through a population using an SIR (Susceptible-Infected-Recovered) model and visualizes the contact network as it builds over time. Each node represents an individual, and edges appear as contacts occur — making transmission chains directly visible in the graph structure.
The simulation begins with a single patient zero (shown in red) and progresses day by day. On each day, every infected individual contacts a random subset of the population. Each contact with a susceptible person has a probability of transmitting the disease. After a set number of days, infected individuals recover and become immune.
Visual Encoding
- Blue nodes — Susceptible individuals who have not yet been infected
- Red nodes (larger, bold border) — Currently infected individuals
- Green nodes — Recovered individuals who are now immune
- Red solid arrows — Contacts where transmission occurred, showing the direction of infection
- Gray dashed lines — Contacts that did not result in transmission
Contact Graph Over Time
As the simulation runs, the network grows with new edges each day. This reveals the contact tracing graph — the complete history of who contacted whom and which contacts led to transmission. Hub nodes with many outgoing red arrows are super-spreaders who infected multiple others.
Timeline Bar
The horizontal bar at the bottom shows the current proportion of the population in each state (blue = susceptible, red = infected, green = recovered), giving an at-a-glance view of epidemic progression.
How to Use
- Start — Click to begin the simulation; click again to pause
- Reset — Stop the simulation and generate a fresh population
- Population — Number of individuals in the network (10–60)
- Contacts/day — How many random people each infected individual contacts per day
- Infection prob — Probability that a contact between an infected and susceptible person results in transmission
- Recovery days — Number of days until an infected individual recovers and becomes immune
- Speed — Milliseconds between simulated days (lower = faster)
Suggested Experiments
- Low transmission: Set infection probability to 0.1 and observe how the disease may die out
- High contacts: Increase contacts/day to 6–8 and watch super-spreader patterns emerge
- Long recovery: Set recovery days to 14+ and observe how longer infectious periods lead to larger outbreaks
- Herd immunity: Watch how recovered (green) nodes create barriers that protect remaining susceptible nodes
Key Concepts Illustrated
SIR Model
The SIR model divides a population into three compartments: Susceptible (can be infected), Infected (can transmit), and Recovered (immune). The basic reproduction number R0 estimates how many secondary infections each initial case produces.
Contact Tracing
The graph structure directly shows the contact network — which individuals were in contact and when. In real epidemiology, reconstructing this graph is essential for identifying transmission chains and breaking them through isolation and quarantine.
Network Effects
The force-directed layout naturally clusters individuals who share many contacts. Densely connected clusters experience rapid local spread, while bridges between clusters enable the disease to reach new groups.
Iframe Embed Code
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