Norovirus infection associated with unusual fatal case of Guillain-Barré syndrome in the community outbreak in Pune, India.

Norovirus (NoV) is a major global cause of acute viral gastroenteritis, responsible for both sporadic infections and widespread outbreaks affecting individuals across all age groups. Although typically self-limiting, gastrointestinal illness, characterized by nausea, vomiting, and diarrhea, recent evidence points to its potential role in causing nonintestinal complications. Central nervous system (CNS) manifestations such as febrile seizures, convulsions, and encephalopathy have been increasingly associated with norovirus, albeit infrequently. During a large Guillain-Barré Syndrome (GBS) outbreak in January-March 2025 in the southwestern region of Pune, India, a 40-year-old male developed progressive weakness of the limbs beginning on January 18th and was admitted to a tertiary care center in a nearby town for evaluation. Molecular testing of stool samples confirmed the presence of Norovirus Group II RNA, while screening for other enteric pathogens, including Campylobacter jejuni (C. jejuni), the most recognized infectious trigger for GBS, was negative. While C. jejuni remains the primary pathogen linked to GBS, our findings support growing speculation about norovirus as an emerging, albeit rare, trigger. Further studies are needed to investigate the underlying mechanisms and to clarify the role of norovirus in GBS pathogenesis, particularly during community outbreaks.