Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 14, No. 11, November 2008 (H), 293 (R), and 295 (N) of the NA protein. In summary, the 12 viruses isolated from this study were similar to the viruses from other sources in Thailand, which indicates that the viruses are endemic to Thailand, are circulating in the country, and can be found in any exposed species. The route of infl uenza virus (H5N1) introduction into the markets remains to be established. We suspect that this contamination might have occurred as a consequence of animal movement from outbreak areas or from viruscontaminated cages, trucks, and equipment. Unfortunately, the original sources of animals in the markets could not be identifi ed because birds from different sources were housed in 1 or several cages. Fortunately, no human infection was found during 2007-2008 in those provinces where the viruses were isolated.