AbstractPoint-of-care detection of pathogens is critical to monitor and combat viral infections. Here, we demonstrate a plasmonic coupling assay (PCA) using gold nanourchins (AuNUs) as labels for the colorimetric quantification of viruses. The antibody functionalized AuNUs allow for rapid and highly specific identification of viruses and provide strong color change for sensitive detection. Using respiratory syncytial virus (RSV) as a target, we demonstrate that the AuNU-based PCA achieves a detection limit of 1,402 PFU/mL (equivalent to 17 copies/μL) that is 3.1- and 5.7-times lower than the rod- and sphere-based counterparts, respectively. The improved detection sensitivity arises from the higher virus binding capability and stronger plasmonic coupling at long distances (∼10 nm) by AuNU probes. The detection can be performed with a portable smartphone-based spectrometer and is validated by testing RSV-spiked nasal swab clinical samples. Our study reports a rapid and sensitive approach for intact virus detection and provides a potential toolkit at the point of care.Graphical abstract