Detection of Highly Pathogenic Avian Influenza A(H5N1) Virus in Cat and Rats during Outbreak in Backyard Poultry, United States, 2025

Abstract

In 2025, highly pathogenic avian influenza A(H5N1) virus was detected in a poultry flock in Illinois, USA. Quantitative reverse transcription PCR, sequencing, and histopathology on cat and rat samples from the farm showed multiple positive tissues and high sequence identity to an avian isolate. Small mammals might contribute to H5N1 transmission.