According to a CDC report from May 2005, tiger-to-tiger transmission likely occurred in Thailand in October 2004, during an H5N1 outbreak at a zoo:
During the second outbreak of avian influenza H5N1 in Thailand, probable horizontal transmission among tigers was demonstrated in the tiger zoo. Sequencing and phylogenetic analysis of those viruses showed no differences from the first isolate obtained in January 2004. This finding has implications for influenza virus epidemiology and pathogenicity in mammals.
Our results demonstrated that tigers kept in captivity are at risk for infection with and dying of the H5N1 virus; moreover, they could be infected by horizontal transmission since raw chicken carcasses represent the main food item for them. Alternative food for the tigers should be considered to reduce the risk for infection. Epidemiologic data obtained from this study demonstrated that all tigers that became ill after October 23, 2004, were probably infected by horizontal transmission since the animals had not been fed raw chicken carcasses since October 16.
The outbreak took place at the largest tiger zoo in Thailand, where a total of 441 tigers lived.