Background Human Respiratory Syncytial Virus (hRSV) is a leading cause of lower respiratory tract infections, particularly affecting infants, older adults, and immunocompromised individuals. The virus exists as two major types, RSV A and RSV B, each with distinct clades that aid in tracking viral evolution. Outbreak timing and severity can differ even within nearby areas, and genetic similarities are often seen across neighboring regions. Ongoing viral evolution poses challenges to long-term vaccine development, underscoring the need for localized genomic surveillance to guide public health efforts. This study analyzed hRSV-positive cases from the Emory Healthcare Microbiology Lab to identify mutations that may impact viral fitness and antigenicity. We summarized the genomic evolution of hRSV during the 2024–2025 season at Emory University Hospital and demonstrated how integrating genomic and clinical data can enhance our understanding of viral adaptation, informing both treatment and vaccine development.

Methods Residual nasal swabs were collected from 182 hRSV-positive adult patients at Emory University Hospital between September 2024 and March 2025. Nucleic acids were extracted, reverse-transcribed to cDNA, and used to generate multiplex RSV amplicon libraries, which were sequenced using Illumina MiSeq or NextSeq platforms (~2 million reads per sample). Genomes were aligned with MAFFT, clades assigned using Nextclade, and mutations analyzed to track potential immune escape variants.

Results

Among RSV A samples, clades A.D.3.1, A.D.5.2, and A.D.1.5 were most prevalent, while RSV B samples were primarily B.D.E.1, with additional cases of B.D.4.1.1 and B.D.E.1.4. In vaccinated individuals (n = 17), infections involved a genetically diverse mix of strains, with B.D.E.1 (24%), B.D.4.1.1 (18%), and A.D.3.1 (12%) being the most common. No single clade predominated among breakthrough infections. Symptom profiles appeared similar between vaccinated and unvaccinated individuals, with the most notable difference being mortality, which was observed only in unvaccinated patients.

Conclusion Our analysis revealed that multiple RSV A and B clades co-circulated during the 2024–2025 season, demonstrating substantial viral diversity across the region. Breakthrough infections among vaccinated individuals were linked to a wide range of clades, with no evidence of a single dominant escape variant. While our findings align with broader regional trends, we also identified distinct local variants, reinforcing the importance of continued, localized genomic surveillance. The study was limited by sample size and scope, highlighting the need for expanded surveillance efforts. Ongoing analyses using Nextclade will focus on identifying prevalent escape mutations driving immune evasion. This genetic diversity in both vaccinated and unvaccinated individuals emphasizes the evolving nature of RSV and the need for adaptive public health strategies and vaccine design.