SHIC’s 100th Milestone Report Exposes Striking PRRSV and Influenza A Deviations

AUSTIN, TX — The Swine Health Information Center (SHIC) has officially released the historic 100th edition of its Domestic Swine Disease Monitoring Report, identifying unexpected summer disease vectors that challenge traditional seasonal expectations.

Compiled through the Swine Disease Reporting System (SDRS), this milestone publication aggregates diagnostic data across major veterinary laboratories to provide a comprehensive analysis of national herd health. The latest findings reveal that despite typical summer seasonal patterns, multiple high-impact pathogens are showing atypical patterns, especially within wean-to-market operations.

Download the detailed report here – SDRS-report-PRRS REPORT

PRRSV Anomaly: Defying Summer Patterns

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) continues to act as a significant economic drag on the U.S. swine market. Historically, PRRSV transmission slows during the late spring and summer months as higher ambient temperatures reduce viral persistence in the environment. However, the 100th SDRS report documents a notable deviation from this trend.

Instead of tapering off, overall PRRSV case positivity has maintained an unseasonal upward trend. This upward trajectory is particularly pronounced in downstream production channels, with wean-to-market site case positivity climbing to nearly 46%. Swine veterinarians note that this sustained high volume of positive cases defies normal cyclical expectations, signaling high underlying viral pressure within growing pig populations.

Influenza A: A Divergent Structural Pattern

While PRRSV challenges historical seasonal baselines, Influenza A Virus (IAV) activity exhibits a striking divergence based on facility type. Overall IAV circulation remains elevated but within expected ranges, though a closer look at the data reveals a clear contrast between breeding herds and finishing populations.

• Adult Sow Farms: Experiencing consistent, encouraging declines in IAV case positivity since the beginning of 2026. This suggests that parental biosecurity practices, maternal vaccination protocols, and herd stabilization strategies are successfully lowering viral loads in breeding herds.

• Wean-to-Market Sites: Experiencing an ongoing, steady rise in active infections since February. Driven by this accumulation of cases, IAV positivity in grow-finish animals peaked at 43%, highlighting a severe breakdown in containment as pigs transition away from maternal immunity.

Biosecurity Consensus: System-Level Decisions Under Scrutiny

In an accompanying veterinary briefing analyzing the milestone report, swine health experts noted that these persistent disease challenges are directly tied to fundamental system-level choices and regional industry infrastructure.

Veterinary clinicians emphasize that the continued spread of highly virulent PRRSV 1C variants cannot be solved purely through individual farm-level adjustments. Instead, the data highlights an immediate, industry-wide need to improve biosecurity and biocontainment strategies at growing sites.

While adult sow farms have historically benefited from significant capital investments in air filtration, strict shower-in facilities, and rigorous transport sanitation, finishing sites are often managed with less stringent protocols. Swine health authorities warn that until grow-finish infrastructure adopts identical biocontainment discipline, downstream sites will continue to act as active viral reservoirs, undermining broader regional elimination efforts.