One Student Comes to School With Flu
How many people catch it, and when is the worst week? Split the school into three groups, write simple rules for how people move between them, and step through the outbreak day by day.
Where this idea comes from
Start here — these are the sources that inspired this exploration.
Introduction
Disease modellers track three groups: people who haven't had the illness, people who have it now, and people who've recovered. Two plain rules connect them — infections need a sick person to meet a healthy one, and sick people recover after a few days. Step those rules forward a day at a time and a whole outbreak unfolds: slow start, frightening middle, burn-out. The 3Blue1Brown simulation and the Washington Post's famous 'flatten the curve' article both come from exactly this model — watch them after you've built your own.
Guiding Questions
- Think it through before any maths: for one new infection to happen today, what has to occur? So what two quantities must tomorrow's new infections depend on?
- Split a class of 25 into three counts — never had it, have it now, recovered. Using your answer above, write tomorrow's three counts in terms of today's, with a number you can tune for how easily it spreads and one for how quickly people recover.
- Step your rules forward a day at a time, starting from one infected student. Plot the three groups. When is the worst day, and why does the outbreak die out even though some people never caught it?
- Next winter won't be identical to your model. Decide what could realistically be different, change it, and report what happens to the worst week.
- Your school keeps absence records. How would you use them to test your model honestly — and what would make you reject it?