October 15, 2025

US swine disease database reveals significant shift in PRRSV patterns 

Data from the US Swine Disease Reporting System's Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Sequencing Database show a shift in detections from 2020 to 2025, with lineage L1A steadily declining while lineage L1C.5 has risen sharply.

Lineage 1A was first detected in the SDRS database in 2006. Since then, it showed a significant increase in the number of detections from 2015 to 2020. However, after 2020, the detections of lineage 1A began to gradually decline.

In 2020, a total of 2,481 sequences were recorded, with the majority belonging to the variants 1A – unclassified (n = 1117) and 1A – 2 (n = 363). By 2025, the total number of detections for lineage 1A had decreased to 839, with the main contributing variants still being 1A – unclassified (n = 296) and 1A – 2 (n = 148). As of 2025, lineage 1A has been detected in 16 distinct states.

Lineage 1H followed a similar trend to lineage 1A, experiencing a decline over the specified period. There were 1,386 detections of lineage 1H in 2020, which peaked in 2022 with 1,617 sequences, but dropped to 454 detections in 2025. The predominant variant during this time was variant 1H.18, which accounted for 192 sequences and was detected in eight distinct states in 2025.

Lineage 1C.5 was first detected in 2020 in the SDRS database, with a total of 161 detections across three distinct states (Indiana, Iowa and Michigan). Since then, there has been a sharp increase in detections from 2020 to 2025, reaching 3,347 in 2025. Notably, the variant 1C.5.32 began to surge after its initial detection in 2023, when there were 72 cases reported in Iowa and Missouri. By 2024, the number of sequences for this variant rose to 1,137, with detections across 10 distinct states. In 2025, the count increased to 1,745 sequences, detected in 13 distinct states.

Alongside the trend observed in lineage 1C.5, the SDRS database also recorded an increase in detections for lineage 1C.2. The number of detections for lineage 1C.2 grew from 117 in 2020 to 604 in 2025. Notably, the majority of these detections were for variant 1C.2, which accounted for 549 sequences identified across 14 distinct states in 2025.

The recent increases in detections of lineage 1C.5 – particularly the expansion of variant 1C.5.32 – coincide with broader shifts in PRRSV sequence patterns across multiple states. The SDRS will continue to monitor PRRSV sequence dynamics to support timely and informed decision making.

-      National Hog Farmer