Classical epidemiological theory associates increased competitive advantage with increasing basic reproduction number, R 0 [27, 28] . The argument is that a larger R 0 results in a faster rate of infection of susceptibles (as determined by the growth rate, r) thereby driving competitor pathogen strains with lower R 0 to extinction. The basic reproduction number varies for different pathogens (and their strains) and varies according to the circumstances (geographic location, age structure, population density, previous exposure etc) of the host population [10] .