How do scientists think that HPAI made its way to North America in the spring of 2015?

• A. Contaminated poultry products imported from China
• B. Infected migratory waterfowl migrating on the East Asia/Australia flyway
• C. Illegal exotic bird smuggling past USDA ports of entry
• D. All of the above

Answer: (B)

Long-distance spread of avian influenza often happens when wild birds move along migratory flyways that connect continents. In spring 2015, the HPAI viruses found in North America carried genetic signatures very closely related to Asian strains and were first detected in wild waterfowl along Pacific-route migration into Alaska and western North America. This pattern, together with the timing during bird migration and subsequent spread into poultry regions, points to introduction via infected wild birds traveling from Asia toward North America rather than being spread primarily by imported poultry products or illegal smuggling. While those other routes are theoretically possible, the available evidence at the time supported the wild-bird, cross-continental movement as the most plausible explanation.