A Virological and Phylogenetic Analysis of the Emergence of New Clades of Respiratory Syncytial Virus

The significant burden of Respiratory Syncytial Virus (RSV) in pediatric and elderly populations is well recognized. However, questions remain about transmission and evolution of RSV in the community, between seasons, and the role played by viral genetics in viral replication. Therefore, we integrated next generation sequencing, patient viral load, and viral replication analysis with surveillance of RSV to initiate a better understanding of viral adaptation in communities. RSV type-A and B infections were most closely related to RSV sequences from the USA and Asia, respectfully. The sample titres between RSV types-A and B were not significantly different. However, when the patient sample titre was compared to the phylogenetics of RSV, emergent clades were identified that we termed High Titre (HiT) clades of RSV. In conclusion, the correlation between patient viral load and replication kinetics of RSV patient isolates in culture indicated that viral genetics may determine virus replicative ability within patients. There was evolution or introduction of high-titre RSV type-A and B infections that seeded HiT clades in the subsequent year. Therefore, virological analysis of RSV isolates in conjunction with RSV phylogenetics may be a tool for predicting new clades of RSV in impending seasons.