The contribution of superinfection events and acute-stage transmissions to the spread of the invader strain.

<p>(A) depicts the time course of the proportion of transmissions of the invader strain that involved superinfection of carriers of the resident virus. Coloured lines show smoothed proportion data for low and high prevalence epidemics using the default scenario, and the “multiple acute” scenario that allowed for repeated peaks of acute-stage infectiousness upon superinfection. In both scenarios, the contribution of superinfection was very low in the low-prevalence setting (green and orange lines), where most individuals were uninfected at the introduction of the invader strain; in contrast, many more transmissions involved superinfection in the high-prevalence setting (purple and red lines). (B) depicts the time course of the proportion of transmissions of the invader strain that originated from acute-stage transmitters in the four cases (colour coding is the same in A and B). (C) shows the difference in the proportion of acute-stage transmissions between the default and the multiple acute scenario for both prevalence settings (i.e. the distance between the red and purple, and between the green and yellow lines of Panel B). Allowing for multiple acute peaks of infectiousness greatly increased the proportion of acute-stage transmissions in the high-prevalence setting (purple line), but to a much lesser extent in the low-prevalence setting (green line). In all cases, time courses are plotted from the introduction of the invader strain into steady-state epidemics of the resident strain. Proportion data were calculated by combining transmission events recorded in 1000 simulation runs, then smoothed by averaging with a sliding window of length 100 weeks. Parameters were set as in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1004093#pcbi.1004093.t001" target="_blank">Table 1</a>; the transmission advantage of the invader strain was 5% in all cases.