In Level 1 of this simulation, you controlled who got sick first, and up to how many people each sick person could infect every day.
As you might guess, these are not all the factors that decide how an infectious disease spreads. Another important factor is when and how long someone is infectious. Sometimes you're not infectious the whole time you are sick. You may stop being infectious before you feel completely better. Or, you may be infectious before you even feel sick.
Here in Level 2, you get to decide how many days after a person gets infected she becomes infectious herself, and for how many days she is infectious. You'll do this by adjusting the "start of infectious period" and "end of infectious period" scrollbars. Just like in Level 1, an infectious person is red, and an immune person is blue. If a person is sick but not yet infectious, the dot is yellow.
Another thing that determines how long an epidemic lasts in a population is how big the population is. You can change the size of the population using the "Board Size" scrollbar.
Things to try:
Choose for each person to infect two others every day. Choose to have the infectious period start on Day 1 and end on Day 3. Start with just one sick person. Run the simulation a few times and watch how long it takes for the epidemic to run its course. Does the length of the epidemic change? On average, how long does it last? Comment in the BBS.
Now, change the infectious period to start on Day 3 and end on Day 6 while keeping everything else the same. Again, run it a few times to get an average length of the epidemic. Is it longer or shorter than before? Any guesses why? Comment in the BBS.
What if you start the infectious period on Day 1 and end it on Day 6? Do you expect the epidemic to last longer or shorter? Give it a try to see if you're right. Comment in the BBS.
Keeping everything else the same, try clicking on the "Board Size" scrollbar. Simulate epidemics in a population with a few people, then try it with larger populations. Given your observations, when an epidemic strikes, what kind of town (big or small) and where in town would you want to live to increase your chances of staying healthy? Comment in the BBS.
