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.

The Wild Felid Advocacy Center in Shelton, Washington, about 80 miles west of Seattle, cares for displaced wild felines, such as cougars, bobcats, servals, tigers, lynxes and more. The nonprofit lost 20 cats since November. Animal health officials confirmed the cause was avian influenza, according to their Facebook.

The animals - including a Bengal tiger, cougars and bobcats - have died of the virus over the past several weeks.