Clinico-Epidemiological Profile and Study of Influenza and Their Subtypes Among Suspected Influenza Patients in a Tertiary Care Teaching Hospital of Vadodara

ABSTRACT Background: Influenza viruses cause significant respiratory illness, with seasonal epidemics and occasional pandemics influenced by antigenic variation. Monitoring local prevalence and subtype distribution is vital for guiding public health responses. Material and methods: A descriptive cross-sectional study was conducted from March to December 2024. A total of 601 throat or nasopharyngeal swabs from suspected influenza cases were collected and tested using the PathoDetect™ multiplex real-time RT-PCR kit, which detects influenza A, B, and subtypes A(H1N1) and A(H3N2). Quality control included internal and external validation. Results: Overall positivity was 20.46%. The highest number of cases occurred in individuals >60 years, while the highest positivity rate was in children <10 years. Fever (78.86%) was the most common symptom; COPD (29.26%) was the leading comorbidity. Influenza A was predominant (92.97%), with H1N1 (53.90%) as the leading subtype, followed by H3N2 (8.59%). Two seasonal Peaks of H1N1 were observed in March–April and August–October. Five co-infections were detected: two with H1N1 and H3N2, and three involving Influenza B co-infected with H1N1, H3N2, and untypable Influenza A. Conclusion: H1N1 is the dominant circulating strain. Findings highlight the need for continuous surveillance, timely diagnosis, and targeted vaccination. Broader community-based studies are recommended for comprehensive influenza control.