Influenza Pandemics Occur Cyclically Because

Question

Influenza pandemics occur cyclically because
A) less than 100% of the population is immunized.
B) new strains emerge due to reassortment between bird, swine, and human variants.
C) the vector is seasonal.
D) there are environmental reservoirs that release the virus during particular seasons.

Accepted Answer

Influenza pandemics occur cyclically because new strains emerge due to reassortment between bird, swine, and human variants. This can lead to the emergence of a virus with pandemic potential, as seen with the H1N1 influenza pandemic in 2009. Other factors such as incomplete population immunity and environmental reservoirs may also contribute to the occurrence of pandemics, but the emergence of new strains through reassortment is the primary reason for cyclicality.