The Wild Felid Advocacy Center in Shelton was home to 37 big cats - including tigers, cougars and leopards - before the outbreak began in late November, said Mark Mathews, who co-founded the sanctuary in 2004. Twenty died from the disease - an even mix of elderly cats with previous medical issues and younger, healthier cats.

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.