Complex Dynamics of the Respiratory Syncytial Virus (RSV) Surge

A surge in respiratory syncytial virus (RSV) infections occurred in the United States in 2022, involving multiple lineages of RSV-A and RSV-B that were shared across geographically distant areas, according to a study published in the New England Journal of Medicine.

“To investigate whether the emergence of a highly transmissible or virulent variant contributed to the surge, we sequenced RSV genomes from a convenience sample of symptomatic patients with RSV infection who presented to Massachusetts General Hospital or its outpatient practices in the greater Boston area in November 2022,” wrote corresponding author Gordon Adams, BA, Massachusetts General Hospital in Boston, MA, and coauthors. Genomic analysis found that 91% of the United States RSV surge in 2022 was driven by multiple RSV-A lineages and 9% by RSV-B. RSV-A genomes were grouped into 10 clades with a most recent common ancestor between 2014 and 2017. RSV-B had a most recent common ancestor in 2019.

The Massachusetts genomes fit into 4 of the 6 clades of publicly available RSV genomes from the 2022 surge in the United States from Washington State.

“These data suggest the 2022 RSV surge in the United States consisted of numerous preexisting viral lineages, many of which were shared between geographically disparate areas, and are inconsistent with the emergence of a single, highly transmissible RSV lineage as the cause of the surge,” the study authors concluded.

Nonviral factors may have also contributed to the surge, including changes in population immunity due to altered RSV dynamics resulting from interventions during the COVID-19 pandemic.

Reference

Adams G, Moreno GK, Petros BA, et al. Viral Lineages in the 2022 RSV Surge in the United States. N Engl J Med. 2023;388(14):1335-1337. doi:10.1056/NEJMc2216153