Twenty big cats, including a half-Bengal tiger and four cougars, died between late November and mid-December at a sanctuary in Washington State after becoming infected with bird flu, according to the facility’s director.

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.

Twenty big cats have died after contracting bird flu at a Washington State animal sanctuary. The Wild Felid Advocacy Center of Washington in the city of Shelton announced the deaths on December 20. Just two weeks prior, officials confirmed the presence of bird flu in the sanctuary, which forced the center to close and quarantine.