A meta-analysis of infant gut viromes reveals global patterns in bacteriophage community assembly and functional capacity over the first three years of life.

Assembly of the gut microbiota in infancy is an important health determinant, yet the viral component, the virome, remains poorly described. Here, we conduct a meta-analysis of 12 infant cohorts across 8 countries to model gut virome development over the first three years of life. Our results revealed distinct diversity patterns, where viral richness increased significantly over the first eight months of life alongside a loss of community evenness. We define virome developmental velocity, the rate of change between sequential samples, which significantly decreased over time. This was mirrored by community-wide convergence, as infant viromes became more similar with age. Functionally, the transition to a stable state involved a significant decrease in extracellular temperate phages and shifts in phage-encoded auxiliary metabolic genes, which can modulate host metabolism. Our work provides a baseline characterization of gut virome development, marked by a conserved successional trajectory, providing a framework to identify disease-associated perturbations.