Evolutionary ecology of virus emergence

Abstract

The cross-species transmission of viruses into new host populations, termed virus emergence, is a significant issue in public health, agriculture, wildlife management, and related fields. Virus emergence requires overlap between host populations, alterations in virus genetics to permit infection of new hosts, and adaptation to novel hosts such that between-host transmission is sustainable, all of which are the purview of the fields of ecology and evolution. A firm understanding of the ecology of viruses and how they evolve is required for understanding how and why viruses emerge. In this paper, I address the evolutionary mechanisms of virus emergence and how they relate to virus ecology. I argue that, while virus acquisition of the ability to infect new hosts is not difficult, limited evolutionary trajectories to sustained virus between-host transmission and the combined effects of mutational meltdown, bottlenecking, demographic stochasticity, density dependence, and genetic erosion in ecological sinks limit most emergence events to dead-end spillover infections. Despite the relative rarity of pandemic emerging viruses, the potential of viruses to search evolutionary space and find means to spread epidemically and the consequences of pandemic viruses that do emerge necessitate sustained attention to virus research, surveillance, prophylaxis, and treatment.

Hidden diversity and evolution of viruses in market fish

“…This finding supports classic epidemiological theory that larger populations that have higher contact rates have an increased likelihood of acquiring and transmitting viruses ( May and Anderson 1979 ). Here, we hypothesised that close contact while shoaling may facilitate virus transmission between fish ( Dennehy 2017 ). It was therefore notable that the most solitary of the fishes we studied here, the largetooth flounder, harboured the smallest number of viral transcripts.…”

“…2008 ; Engering et al. 2013 ; Dennehy 2017 ). Although theory suggests that host population density is central to viral spread and epidemic potential ( Anderson and May 1982 ), few studies have determined the effect of density-dependent transmission in natural host systems.…”

Onward transmission of viruses: how do viruses emerge to cause epidemics after spillover?

“…We are rapidly gaining new insights into the complexities of viral sequences and their structures, as well as the roles of low-level polymorphisms as substrates for rapid evolution [ 69 – 71 ]. As described above, and reviewed elsewhere [ 72 , 73 ], the emergence of new epidemic viruses requires host adaptive mutations, recombination or reassortment, or the acquisition of modifications and accessory genes. Retrospective analysis indicates that those changes occur during the early stages of infection and spread in the new host or within an intermediate host, and that those are required to give increased replication and transmission.…”

Heteroaggregation of an enveloped bacteriophage with colloidal sediments and effect on virus viability

“…φ6 is a dsRNA virus whose host cell is Pseudomonas phaseolicola, a common plant pathogen. φ6 consists of an icosahedral nucleocapsid surrounded by a bi-lipid envelope and is therefore employed as a model for virus emergence in evolutionary studies and for human pathogens such as coronavirus (Dennehy, 2017;Mindich, 2004). The diameter of φ6 is~80 nm.…”