Which statement about Avian Influenza is true?

• A. It refers to a collection of virus strains, not all of which cause disease in people.
• B. It is caused by a single virus strain.
• C. It does not have multiple H and N types.
• D. It only affects birds and never humans.

Answer: (A)

Avian Influenza is a group of influenza A viruses that circulate in birds, not a single virus. There are many strains, defined by combinations of surface proteins called hemagglutinin (H) and neuraminidase (N), producing a wide range of H and N types. Because of this diversity, some strains cause disease primarily in birds, while only a subset have the potential to infect humans, and not all of those cause illness in people. That makes the statement that Avian Influenza refers to a collection of virus strains, not all of which cause disease in people an accurate description.

The other ideas aren’t correct because it is not a single virus strain, it does have multiple H and N types, and it can infect humans in certain circumstances. It also does not affect only birds; humans can become infected in some exposures.