What animals are considered the reservoir for influenza A viruses?

• A. Domestic chickens and turkeys
• B. Feral swine
• C. Waterfowl and shorebirds
• D. Asian backyard poultry flocks

Answer: (C)

Influenza A viruses persist and circulate primarily in wild aquatic birds, with waterfowl and shorebirds acting as the main reservoir. These birds harbor a wide diversity of viral subtypes and shed the virus into water and sediments, allowing the virus to persist in the environment and spread along migratory flyways to domestic poultry and other species. Domestic chickens and turkeys can become infected and amplify outbreaks, but they are not the natural reservoir in nature. Feral swine and Asian backyard poultry flocks can harbor the virus, yet they are not the primary reservoir; they are more often incidental hosts or bridge hosts. Therefore, waterfowl and shorebirds are the best answer because they represent the natural reservoir for influenza A viruses.