This week we’ve looked at the outbreak of Swine Flu and examined just how easily it could spread through London. We follow the fictional journey of John, a self-absorbed Londoner, on his Twitter page and count the number of people he directly infects on his return from a holiday in Mexico.

So over 400 people are directly infected by John before he is quarantined, with over 100 infections via the London Transport System alone. A sobering thought next time you’re on your way to work. The estimates in our fictional blog are based on a SIR (Susceptible – Infected – Recovered) model of flu infections, calibrated using parameters from the Hong Kong flu virus and overlaid with facts and assumptions about John’s journey and the number of people he is likely to contact. There are some unknown characteristics about the flu virus that make estimating its eventual spread very uncertain, and small changes in the assumptions used to estimate the unknowns can have very large consequences in the final outcome. For example, without quarantining or inoculating, it would be possible for John (and those he has directly and indirectly infected) to contaminate the majority of Londoners within just a few weeks, yet rapid quarantining could contain the problem quite effectively. Maybe time to take some personal responsibility – Tamiflu, anyone? Thanks to Dave Lee and Neal Mistry for the topic, analysis and tweeting story telling method. Have a good (and 38% longer) weekend.