Pre-existing immunity from seasonal influenza strains may provide some partial protection if an avian influenza virus such as H5N1 infects humans.
November 06, 2025
medium
general
Cross-protection from prior seasonal influenza exposures can influence human susceptibility to novel influenza viruses.
The Centers for Disease Control and Prevention estimates that seasonal influenza causes about 52,000 deaths, about 41 million illnesses, and about 710,000 hospitalizations annually in the United States.
high
statistical
These figures are recurring annual burden estimates for seasonal influenza in the U.S.
Coinfection of a person with seasonal influenza and an avian influenza virus can enable genetic reassortment that could produce an avian-derived influenza virus with increased ability to transmit between people.
high
epidemiological
Virological risk from simultaneous infection with different influenza viruses.