Orcine reproductive and respiratory syndrome virus-2 (prrsv-2) impacts ~30-50% of swine breeding farms in the U.S. Annually, with newly evolved genetic variants of the virus causing recurrent epidemic…

The Department of Agriculture National Institute of Food and Agriculture awarded the Regents of the University of Minnesota $2.811 million on February 1, 2026, under the Agriculture and Food Research Initiative (AFRI) program to conduct research on porcine reproductive and respiratory syndrome virus-2 (PRRSV-2) fitness and virulence dynamics.

The research will build a multi-scale understanding of how virulence and transmissibility interact to determine viral fitness at pathogen, host, and population scales. The team will analyze more than 50,000 genetic sequences to estimate epidemiological fitness of PRRSV-2 genetic variants at national scales, correlate fitness to disease severity in real-world farm populations using weekly production data from infected farms, and conduct in vivo and in vitro experiments to quantify transmission, replication, and virulence at host and cellular levels. This work will provide American producers with standardized benchmarks of disease virulence and early warning identification of high-impact variants to enhance economic competitiveness of U.S. agriculture by informing vaccine development and control strategies targeted at highly fit variants. PRRSV-2 impacts approximately 30–50 percent of swine breeding farms in the U.S. annually and costs the industry approximately $1.2 billion per year.

Performance occurs in Minneapolis, Minnesota through January 31, 2030. The University of Illinois, through the Board of Trustees of the University of Illinois, received a sub-award dated April 21, 2026, to conduct research on fitness-virulence trade-offs across pathogen, pig, and population scales for PRRSV-2 genetic variants.

Orcine reproductive and respiratory syndrome virus-2 (prrsv-2) impacts ~30-50% of swine breeding farms in the U.S. Annually, with newly evolved genetic variants of the virus causing recurrent epidemic waves. For rapidly evolving viruses such as prrsv-2, the fitness of different genetic variants drives epidemiological and evolutionary dynamics because more fit variants outcompete others and spread more widely, driving genetic shifts in the virus population across time. Fitness is quantified as the ability to replicate efficiently in cells, transmit rapidly between hosts, or increase in frequency in the population. Higher within-host replication increases both transmissibility and harm caused to the host (i.e., virulence), which theoretically creates a fitness-virulence tradeoff wherein fitness is optimized at intermediate virulence levels. We build a multi-scale understanding of how virulence and transmissibility interact to determine viral fitness at the pathogen, host, and population scales. Analyzing >50,000 genetic sequences, we will estimate the epidemiological fitness of genetic variants at national scales. Using weekly production data from farms infected with low/high-fitness variants, we will correlate fitness to disease severity in real-world populations. In vivo and in vitro experiments will further quantify transmission, replication, and virulence at host and cellular levels. This project will provide american producers with standardized benchmarks of disease virulence and identification or even early warning of high-impact variants. Given that prrsv-2 costs the industry ~$1.2 billion annually, this research will enhance the economic competitiveness of U.S. Agriculture by generating new knowledge informing vaccine development and control strategies targeted at highly fit variants.