Sample-level PRRSV RT-PCR prevalence in pigs in mainland China (2004-2025): A systematic review and meta-analysis.

Porcine reproductive and respiratory syndrome virus is associated with substantial costs for the global pig industry. We conducted a systematic review and meta-analysis of 71 cross-sectional surveys (307,863 pig specimens from 27 provinces, 2004-2025) to quantify long-term spatiotemporal trends and associated factors of sample-level PRRSV RT-PCR positivity in mainland China. The overall pooled PRRSV RT-PCR positivity was 32% (95% CI: 29-34%) with high between-study heterogeneity (I² = 99%, P < 0.001); this estimate summarizes diverse study populations and does not represent uniform national prevalence. Pooled prevalence declined from 36% (95% CI: 31-41%) in 2004-2015-26% (95% CI: 23-29%) in 2016-2025, potentially driven by shifts in study design and sampling populations. Higher prevalence was associated with South China, small-scale farms, finishing pigs and summer sampling. Funnel plot asymmetry and Egger's test indicated significant small-study effects, likely reflecting publication bias and study heterogeneity. These findings confirm widespread PRRSV detection in sampled pig populations, with a temporal decline and identifiable putative risk factors associated with heterogeneity. Results provide a reference to optimize future PRRSV surveillance and control.