Influenza A virus is a significant respiratory pathogen affecting various species, including swine. The dynamics and diversity of IAV require ongoing surveillance to enhance understanding and generate solutions for control. A recent publication, led by PhD student Dr. Daniel Moraes under mentorship of Swine Disease Reporting System Principal Investigators Drs. Giovani Trevisan and Daniel Linhares at Iowa State University, reported influenza surveillance data gathered from the SDRS, a project funded by the Swine Health Information Center. Published in Frontiers of Veterinary Science in April 2025, results detail 20 years of compiled veterinary diagnostic laboratory data on IAV and provides unique insight into understanding its epidemiology.
Using a comprehensive approach, this study aimed to characterize the macroepidemiological patterns of IAV detection utilizing PCR assays, including subtype identification, over the last 20 years. The findings offer valuable insights into IAV dynamics across the US, detailing its distribution by age category, specimen type, and seasonal trends. Specifically, samples submitted between January 2004 and December 2024 to VDLs participating in the SDRS were analyzed and revealed a substantial 31% of the 372,659 samples tested positive for IAV RNA.
Regarding sample types tested for IAV, oral fluids (44.1%) and lung tissue (38.7%) emerged as the most frequently submitted sample types, indicative of their utility in surveillance. Notably, the wean-to-market category exhibited a higher positivity rate at 34.4% compared to the adult/sow farm category’s 26.9%, emphasizing the importance of this age group in IAV ecology. A similar phenomenon has been previously reported for PRRS and PED viruses. The study also revealed a consistent seasonal pattern, with IAV detection peaking in spring and fall and decreasing during the summer months.
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