In this episode of the SwineTime podcast, host and swine veterinarian, Dr. Spencer Wayne, is joined by Dr. Kim VanderWaal from the University of Minnesota to tackle a complex but critical topic for pig farmers: PRRS virus classification.

Dr. VanderWaal is an associate professor in Veterinary Population Medicine with expertise in swine disease ecology, epidemiology, and big data research. She has spent nearly a decade studying swine viruses, particularly PRRS (Porcine Reproductive and Respiratory Syndrome)—one of the most costly and persistent diseases in pork production. With more than 80,000 virus sequences collected in the U.S., researchers now have a wealth of genetic data to study how PRRS evolves and spreads.

The discussion highlights how the industry has shifted fromthe old RFLP typing system, which often gave confusing or misleading results, to a new framework built around lineages, sub-lineages, and variants. This updated approach offers veterinarians and producers more consistent, accurateinformation to evaluate outbreaks and determine whether a farm is facing a repeat infection or something entirely new.

Dr. VanderWaal also explains why some PRRS variants—like the well-known 1C.5 strain—spread so aggressively. These viruses require only a tiny infectious dose to jump between pigs, making traditional biosecurity measures more difficult to hold. The conversation further explores how new viruses emerge, whether through gradual mutation or recombination, when pigs carry multiple strains at once.

For farmers, veterinarians, and others in the swine industry, this episode offers valuable insight into how PRRS is studied, why accurate classification matters, and how ongoing research is equipping the industry to better respond to emerging health challenges.