Virus population bottlenecks during within-host progression and host-to-host transmission

Despite rapidly growing to immense sizes, virus populations suffer repeated severe bottlenecks, both within hosts and when transmitted from host to host. The potential effect of bottlenecks has been theoretically and experimentally documented, but formal estimations of their actual sizes in natural situations are scarce. Bottlenecks during colonization of organs and during transmission are influenced by those occurring at the cellular level. The study of the multiplicity of cellular infection (MOI) thus appears central, and this trait may be differentially regulated by different virus species. The values of MOI and their putative regulation deserve important future efforts, in order to disentangle the complex interactions between the control of gene copy numbers and the populations dynamics/genetics of viruses.

► Demographic fluctuations are of great importance in the evolution of viruses. ► Viral populations can be submitted repeatedly to drastic bottlenecks, both when progressing within a host and when transmitted from host to host. ► Viruses may regulate these bottlenecks through the control of the multiplicity of cellular infection. ► The viral control of MOI may be submitted to trade-offs on the impacts of gene copy number variation and population dynamics.