Which influenza type primarily infects humans and is not typically found in animals?

Which influenza type primarily infects humans and is not typically found in animals?

• A. Influenza A (Flu A)
• B. Influenza B (Flu B)
• C. Influenza D (Flu D)
• D. Influenza C (Flu C)

Answer: (B)

The key idea is how each influenza type differs in which species it typically infects. Influenza A has a broad host range, circulating in humans but also in many animals like birds and pigs, so it isn’t restricted to humans. Influenza B, by contrast, is mainly a human virus and isn’t typically found in animals in nature. Influenza C can infect humans and some animals, but it doesn’t have a strong animal reservoir like influenza A, and it causes milder illness. Influenza D is predominantly found in cattle and is not a common human pathogen. Because influenza B is the type most closely associated with humans and lacks a significant animal reservoir, it’s the best choice for a virus primarily infecting humans and not typically found in animals.

The key idea is how each influenza type differs in which species it typically infects. Influenza A has a broad host range, circulating in humans but also in many animals like birds and pigs, so it isn’t restricted to humans. Influenza B, by contrast, is mainly a human virus and isn’t typically found in animals in nature. Influenza C can infect humans and some animals, but it doesn’t have a strong animal reservoir like influenza A, and it causes milder illness. Influenza D is predominantly found in cattle and is not a common human pathogen. Because influenza B is the type most closely associated with humans and lacks a significant animal reservoir, it’s the best choice for a virus primarily infecting humans and not typically found in animals.