Key Messages 1. Causal attributions for highly pathogenic avian influenza (HPAI) of the H5N1 virus among live poultry, consumers, retailers and breeders in Vietnam, Thailand, Guangzhou and Hong Kong were studied. 2. Three main themes embodying lay explanation for the causes of H5N1 HPAI emerged: viruses, husbandry-related factors, and vulnerability factors. 3. A deeper understanding of the perceptions of risks, biases, causal attributions, and both the facilitators and barriers to change is needed for planning effective changes in health related behaviour.published_or_final_versio