Norovirus Genomes Detected from the Guillain Barre Syndrome (GBS) Cases in a Community Outbreak in Pune, India, 2025

Abstract

Background: In 2025, Pune, India, witnessed an unprecedented surge in Guillain-Barré Syndrome (GBS) cases, raising urgent public health concerns. GBS, a rare neurological condition often linked to infections, demanded immediate epidemiological and molecular scrutiny. Evidence from earlier studies points to infectious agents like Campylobacter jejuni, cytomegalovirus, and enteric viruses as common triggers. Environmental conditions and regional pathogen variations were considered potential contributors to the outbreak. To uncover the cause, a broad molecular screening was initiated to detect any known or emerging infectious agents. 

Methods: A comprehensive molecular screening was conducted for 19 pathogens, including established GBS-linked and enteric pathogens. Advanced genomic techniques, including phylogenetic and recombination analysis, were employed to characterize the detected pathogens.

Results: Two major pathogens, Campylobacter jejuni and Norovirus, were identified by using molecular methods. Phylogenetic analysis revealed that all norovirus strains from GBS patients clustered within genogroup II (GII.16). Recombination analysis showed significant genetic exchanges between the GII.P16/GII.4 and GII.P16/GII.16 genotypes in the GBS-associated norovirus strains, emphasizing recombination as a key factor in viral evolution. In contrast, norovirus strains from non-GBS diarrheal cases displayed no distinct pattern, with a random distribution across multiple genogroups. Genomewide mutation analysis identified lineage-specific adaptations, including unique nonsynonymous mutations in the viral RdRp (RNA-dependent RNA polymerase) and VP1 (major capsid protein) genes, likely driven by immune selection pressures. 

Conclusion: These findings highlight the importance of genomic surveillance to identify emerging norovirus lineages and their potential clinical significance. Continued monitoring is vital to understand norovirus evolution and its possible connection to GBS. 

Keywords: GBS, norovirus, recombinant strains, gastrointestinal illness, viral infections, public health, phylogenetic