Mechanistic modelling of the three waves of the 1918 influenza pandemic

Influenza pandemics through history have shown very different patterns of incidence, morbidity and mortality. In particular, pandemics in different times and places have shown anywhere from one to three “waves” of incidence. Understanding the factors that underlie variability in temporal patterns, as well as patterns of morbidity and mortality, is important for public health planning. We use a likelihood-based approach to explore different potential explanations for the three waves of incidence and mortality seen in the 1918 influenza pandemic in London, England. Our analysis suggests that temporal variation in transmission rate provides the best proximate explanation and that the variation in transmission required to generate these three epidemic waves is within biologically plausible values.