Which of the following best describes the species commonly associated with zoonosis of Type A influenza?

• A. Waterfowl
• B. Pigs
• C. Waterfowl and pigs
• D. Dogs

Answer: (C)

Influenza A viruses have animal reservoirs and the species most closely tied to zoonosis involve birds and pigs. Waterfowl are natural reservoirs for a wide range of influenza A subtypes, widely shedding the virus into the environment. Pigs, on the other hand, can be infected with avian, swine, and human strains and can act as mixing vessels where reassortment occurs, producing new strains that can spill over into humans. This combination makes both waterfowl and pigs the best description for species commonly associated with zoonosis of Type A influenza. Dogs are not typically viewed as a primary source for zoonotic influenza A in the same way.