All cats were infected with H5N1 virus and exhibited clinical signs of disease (fever, lethargy, labored breathing, etc.), and virus was detected in throat, nasal, and rectal swabs, regardless of the original site of infection. Most interesting, virus spread throughout the organ systems with virus being found in respiratory and digestive tracts, liver, kidney, heart, brain, and lymph nodes. Furthermore, examination of infected tissues revealed cellular damage at sites containing viral proteins, providing an explanation for the increased severity of disease in humans.