Which influenza type can spread in both humans and animals and includes subtypes like H1N1 and H3N2 circulating in humans?

Which influenza type can spread in both humans and animals and includes subtypes like H1N1 and H3N2 circulating in humans?

• A. Influenza B
• B. Influenza A
• C. Influenza C
• D. Influenza D

Answer: (B)

Influenza A is the only type that can spread across a wide range of hosts, including humans and various animals, and it carries many subtypes defined by the combinations of the surface proteins hemagglutinin (H) and neuraminidase (N). The subtypes H1N1 and H3N2 are classic examples circulating in humans, reflecting the virus’s capacity for genetic reassortment between human and animal strains and driving seasonal epidemics and occasional pandemics. Influenza B mainly infects humans (and some seals) and does not have the H/N subtype system; its genetic diversity is far more limited. Influenza C also infects humans and animals but causes milder illness and does not have H/N subtypes. Influenza D mostly affects cattle and is not a common human pathogen. Therefore, the type that fits both cross-species spread and the H1N1/H3N2 human subtypes is influenza A.

Influenza A is the only type that can spread across a wide range of hosts, including humans and various animals, and it carries many subtypes defined by the combinations of the surface proteins hemagglutinin (H) and neuraminidase (N). The subtypes H1N1 and H3N2 are classic examples circulating in humans, reflecting the virus’s capacity for genetic reassortment between human and animal strains and driving seasonal epidemics and occasional pandemics.

Influenza B mainly infects humans (and some seals) and does not have the H/N subtype system; its genetic diversity is far more limited. Influenza C also infects humans and animals but causes milder illness and does not have H/N subtypes. Influenza D mostly affects cattle and is not a common human pathogen. Therefore, the type that fits both cross-species spread and the H1N1/H3N2 human subtypes is influenza A.