Risk Assessment of High Pathogenicity Avian Influenza Virus Introduction into Poland via Legal Importation of Live Poultry

The risk of highly pathogenic avian influenza (HPAI) virus introduction via import of live poultry results from the probability that infected birds are exported from apparently HPAI-free areas during the silent phase of the epidemic, i.e., the period between an incursion of the virus into a susceptible population and a report on the outbreak by an exporting country. In our study we adapted a stochastic model, previously published in 2010 by Sánchez-Vizcaíno et al., with our own modifications in which the probability of HPAI introduction was assessed as the sum of the probabilities of entry of at least one infected bird from each susceptible species exported from each country into each Polish region (county). The mean annual probability of HPAI introduction into Poland via legal trade of live poultry was very low (3.07 × 10(-3), which corresponds to 1 outbreak every 326 yr). The highest risk was associated with the import of turkeys (62%) and chickens (33%). The exporting countries that contributed the most to the overall risk were Italy (31%), the Netherlands (24%), and the Czech Republic (17%). The risk was not evenly distributed across the country and it seemed higher in western, north-central, and eastern Poland while several counties of the north-west, central, or south-east parts of the country were at negligible risk. The applied model provides quantitative evidence that the risk of HPAI introduction through legal trade of poultry does not play a major role and that other paths, such as wild birds migrations or illegal trade, should be considered as the most-likely routes along which the virus can be introduced.