A wildlife sanctuary in Washington state is under quarantine after 20 big cats died due to H5N1 bird flu infections.

Bird flu has been on the rise in Washington state and one sanctuary was hit hard: 20 big cats – more than half of the facility’s population – died over the course of weeks.

Nearly two dozen big cats died after bird flu swept through the sanctuary where they lived. The Wild Felid Advocacy Center near Shelton, Washington said the first animals died last month but the cause was just recently confirmed, KIRO reported. In all 20 cats died, more than half of the sanctuary’s big cats.