Viral phylodynamics
![Figure 1. Idealized caricatures of virus phylogenies that distinguish between exponential growth (A) and constant size (B) of the virus population.](/Images/godic/202502/02/Viral_Phylodynamics_Wm_population_size_bw.svg4647.png")
![Figure 2. Idealized caricatures of virus phylogenies that show the effects of population subdivision, distinguishing between a structured host population (A) and an unstructured host population (B). Red and blue circles represent spatial locations from which viral samples were isolated.](/Images/godic/202502/02/Viral_Phylodynamics_Wm_spatial_structure_migration.svg4647.png")
![Figure 3. Idealized caricatures of virus phylogenies that show the effects of immune escape where selection results in an unbalanced tree (A) and neutral dynamics results in a balance tree (B).](/Images/godic/202502/02/Wm_selection_tree_bw.svg4648.png")
![Figure 4. A gene genealogy illustrating internode intervals.](/Images/godic/202502/02/Tree_epochs.svg4648.png")
Viral phylodynamics is defined as the study of how epidemiological, immunological, and evolutionary processes act and potentially interact to shape viral phylogenies. Since the coining of the term in 2004, research on viral phylodynamics has focused on transmission dynamics in an effort to shed light on how these dynamics impact viral genetic variation. Transmission dynamics can be considered at the level of cells within an infected host, individual hosts within a population, or entire populations of hosts.