For American pig farmers, the threat of porcine reproductive and respiratory syndrome virus (PRRSV-2) is a constant shadow. The virus is a devastating double threat: it triggers late-term miscarriages in sows and severe pneumonia in young piglets. Every few years, a new strain of the virus evolves and sweeps across farms, causing devastating losses in its wake. And some signs suggest that new strains are increasingly severe.
With the U.S. swine industry losing roughly $1.2 billion every year to this single pathogen, researchers are now turning to big data and evolutionary biology to get ahead of the next outbreak, aiming to protect both the livelihoods of farmers and the well-being of the animals in their care.
Backed by a new $2.8 million grant from the USDA National Institute of Food and Agriculture (NIFA), a team led by the University of Minnesota College of Veterinary Medicine (CVM) is launching a massive effort to understand viral "fitness.” Just as a triathlete must balance speed and endurance, a virus must balance its ability to rapidly replicate inside a host with its ability to persist long enough to spread to the next farm. This project aims to find the sweet spot where the virus is most dangerous and use that data to understand why some new variants are more likely to become the next national epidemic.
“By measuring what drives high fitness and virulence across PRRSV-2 variants, we can anticipate whether a new variant is likely to quickly outcompete older ones and if more aggressive control measures, such as removing infected herds, are warranted,” describes Kim VanderWaal, AGREETT-funded CVM associate professor and one of the co-leads of the project.
The research starts with genetic detective work. By analyzing a massive library of more than 50,000 genetic sequences of the virus, they are tracking how it has evolved over time and identifying variants that are both winners and losers from an epidemiological fitness perspective. They’ll then take this work beyond databases, connecting to real-world production data from farms experiencing outbreaks caused by those winners and losers to better understand how fitness relates to the severity of outbreaks.
To connect the patterns they see in the data to biology, the team will also conduct controlled laboratory experiments. These studies allow researchers to observe the virus in controlled settings to measure exactly how efficiently it replicates and how easily it jumps from one host to another. This "multi-scale" approach allows them to see exactly how a tiny mutation in the virus’s genetic code translates to fever, respiratory distress, or loss of life in the barn. By mapping these genetic markers to clinical impacts, the team can better understand, predict, and control the impact of the most dangerous strains of the virus.
One of the project’s most ambitious goals, then, is to create a standardized benchmark for virulence. Currently, when a new strain appears, producers often don't know how much of a threat it poses until it has already spread through their region. By identifying the traits that make a variant "highly fit"—meaning it spreads fast and hits hard—the team hopes to provide an early-warning system that tells farmers exactly what they are up against.
“I’m excited about the team we have assembled to tackle this research,” VanderWaal says. In addition to the seasoned collaboration between VanderWaal and her co-investigator, CVM professor Declan Schroeder, new collaborators on the project include CVM assistant professors Mariana Kikuti and Igor Paploski, who will lead the field component of the project, and Federico Zuckermann at the University of Illinois, who will lead in vitro assessments of the virus's capabilities.
Ultimately, the research aims to improve animal health and fortify the resilience of the American food supply. By understanding the evolutionary "logic" of PRRSV-2, the team is providing the tools necessary to develop better vaccines and smarter control strategies. In a race against a rapidly evolving enemy, this $2.8 million investment is a crucial step toward a future where a virus’s next move is no longer a surprise.
This article originally appeared in the Spring 2026 issue of the College of Veterinary Medicine's profiles publication.