The 2022 RSV surge was driven by multiple viral lineages

Area of Science:

• Virology
• Genomics
• Epidemiology

Background:

• The US experienced an unusually early and severe respiratory syncytial virus (RSV) surge in autumn 2022.
• The underlying factors contributing to this surge remain largely unknown, prompting investigation into viral characteristics.

Approach:

• Sequenced 105 RSV-positive specimens from symptomatic patients in the Greater Boston Area.
• Conducted genomic analysis on 77 RSV genomes (RSV-A and RSV-B).
• Performed phylogenetic analysis to determine the evolutionary history and relationships of circulating RSV strains.

Key Points:

• The 2022 RSV surge was driven by multiple, diverse lineages of both RSV-A (91%) and RSV-B (9%).
• Phylogenetic analysis indicated that the clades responsible for the surge emerged well before the COVID-19 pandemic, with estimated times to most recent common ancestor (tMRCA) between 2009 and 2019.
• The evolutionary rates of the sequenced RSV-A and RSV-B genomes were consistent with established estimates, suggesting no accelerated evolution.

Conclusions:

• The polyphyletic nature of the RSV genomes observed during the 2022 surge contradicts the hypothesis of a single, highly transmissible novel lineage driving the epidemic.
• The surge was likely a result of the simultaneous circulation of multiple established RSV lineages, potentially influenced by factors other than viral evolution.