Which influenza type is most severe and the only one known to cause pandemics?

Which influenza type is most severe and the only one known to cause pandemics?

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

Answer: (A)

Pandemics arise when a novel influenza A virus with a drastically different surface protein combination emerges and spreads globally. Influenza A has many animal reservoirs and can undergo major genetic reassortment (antigenic shift), creating new subtypes that people have little to no immunity against. This ability to suddenly change and jump between species is what enables pandemics and can lead to severe outbreaks, depending on the strain. In contrast, influenza B mainly circulates among humans and does not undergo the same dramatic shifts that drive pandemics, influenza C usually causes mild illness and doesn’t spread widely enough to cause pandemics, and influenza D primarily affects cattle and is not established as a human pathogen. Thus, influenza A is the one known to cause pandemics and can be associated with severe disease.

Pandemics arise when a novel influenza A virus with a drastically different surface protein combination emerges and spreads globally. Influenza A has many animal reservoirs and can undergo major genetic reassortment (antigenic shift), creating new subtypes that people have little to no immunity against. This ability to suddenly change and jump between species is what enables pandemics and can lead to severe outbreaks, depending on the strain. In contrast, influenza B mainly circulates among humans and does not undergo the same dramatic shifts that drive pandemics, influenza C usually causes mild illness and doesn’t spread widely enough to cause pandemics, and influenza D primarily affects cattle and is not established as a human pathogen. Thus, influenza A is the one known to cause pandemics and can be associated with severe disease.