Excerpt:

The first signs of the bird flu outbreak appeared when a mysterious illness began spreading among cats in June.

On June 18, a vet in western Poland reported the death of a cat that had suffered from neurological and respiratory symptoms, BNO News, a Dutch news agency, reported. Since then, dozens of cases of this unusual illness—many resulting in death—were reported across the country.

Local media reports indicated that the disease had a sudden onset and progressed very rapidly.

“The animals die in a short time,” Paulina Grzelakowska, director of the Tri-City Veterinary Clinic in Gdańsk, in northern Poland, told broadcaster TVN24. “Cats of all ages are affected, both pedigree and nonpedigree, those kept indoors and outdoors, those vaccinated against infectious diseases and those that have not been vaccinated.”

Early testing in the past few days subsequently identified the H5N1 virus in samples taken from some of the dead cats.