Epidemics and topology
Below is a graph of cases and spread against days elapsed from the initial WHO report, for the current A(H1N1) flu outbreak. These graphs are derived directly from the WHO published figures. The number of countries reporting cases and reported deaths are plotted against the secondary right hand axis.
One of the interesting features about real world epidemics (and pandemics) is that they don’t follow a nice smooth logistics curve with a period of slow growth followed by an explosive growth phase then eventually plateauing out in the final burnout phase. In practice there may be waves of infection over a period of time. While there are certaintly biological reasons for this, a more fundamental reason may simply be the complex topology of the percolating cluster (see earlier post), where local clusters and scale free distributions may cause significant changes in the behaviour of an outbreak over time. For those interested in looking at the raw data, see the daily updates available on the WHO A(H1N1)website.