Fig. 4
From: Longitudinal piglet sampling in commercial sow farms highlights the challenge of PRRSV detection
FARM D. PRRSV RNA detection (
,
) by week (W), farrowing room (R), and specimen (P - processing fluid, F - family oral fluid).). aNo. RNA positive samples (+) and no. samples collected (∑). 
PRRSV RFLP 1–7-4 detected