Evolutionary rescue effect disappears under more realistic assumptions

In a recent paper Zhang et al. [1] elegantly incorporate the evolution of inter-host virus fitness into an epidemiological model. They show that this leads to substantial changes in the system dynamics and in particular that evolution can “rescue” the pathogen population if the mutation rate is high enough. However, their model rests on the assumption that mutations that affect inter-host fitness are neutral on average. Here we show that under more realistic assumptions concerning the fitness distribution of mutations, the effect can easily disappear and higher mutation rates in fact reduce the likelihood of a pandemic.