The evolution of H5N1 HPAI viruses by reassortment with LPAI viruses in the aquatic bird reservoir played an important part in the genesis of the multiple genotypes, clades, and subclades of Asian H5N1 HPAI viruses and is ongoing. 37 However, it is the ever-increasing poultry industry that provides the reassortment interface between wild and domestic avian species. The number of domestic ducks, chickens, and other poultry continues to increase, but biosecurity and separation of species is not always taken into account. Ducks raised in a closed high-biosecurity system in Thailand were protected from infection while H5N1 HPAI viruses were circulating among backyard ducks, open house ducks, and grazing ducks. 4 Therefore, biosecurity can prevent the spread of influenza viruses from wild to domestic ducks.