Avian influenza A(H3N8) viruses are some of the most commonly detected subtypes in wild birds and have been found in live poultry markets in Asia, causing little to no sign of disease. Spill-over infections of A(H3N8) avian influenza viruses have been reported in mammals, including dogs, seals, and horses. Transmission to humans is sporadic, and the result of direct or indirect exposure to infected live or dead poultry or contaminated environments.