New Monthly PRRSV Variant Report Launches with SHIC Support

A new national surveillance effort enhances decision-making in swine health by identifying and communicating emerging PRRSV variants. Dr. Mariana Kikuti, recently appointed assistant professor at the University of Minnesota, is leading the development of the PRRSV Variants Under Monitoring (VUMs) Monthly Report in collaboration with the SHIC-funded Morrison Swine Health Monitoring Project and the PRRS-Loom analytical platform. The report, launched in August 2025, is designed to give producers and veterinarians an early warning of potential threats, improving preparedness and coordinated response across the industry. 

This initiative utilizes the PRRS-Loom tool, a machine-learning model that analyzes 603 ORF5 bases to classify viruses by lineage, sublineage, and variants. These classifications are combined with a forecasting algorithm that anticipates whether a variant is likely to expand significantly, defined as more than a 20% increase in the next year, based on retrospective data with 77% accuracy (Pamornchainavakul et al., 2024). When integrated with the near real-time MSHMP data, the approach allows the new report to identify where specific PRRSV variants are already present and estimate their potential for wider spread. 

PRRSV variants are defined as closely related viruses based on ORF5 gene similarity, typically differing less than 2.5% within a variant and 5% from the nearest related variant. VUMs specifically represent PRRSV-2 variants circulating in the US that show genetic and epidemiologic indicators of wider transmission. To highlight urgency and guide responses, VUMs are categorized into four levels according to the number of sites impacted over the past six months:

• Level 1 involves up to 30 sites
• Level 2 involves 31–50 sites
• Level 3 involves 51–100 sites
• Level 4 involves >100 sites

Reports for Level 2 or higher VUMs will include expanded epidemiological discussion, examining affected sequences, sites, systems, and states. These summaries will be accompanied by epidemiological curves showing variant dynamics over time and situation reports that provide context for ongoing industry response. Together, these tools give stakeholders greater situational awareness, helping veterinarians and producers adjust strategies before a variant reaches wider distribution.