Which viruses are unique because of their ability to alter antigenic composition, thus reinfecting "nonimmune" susceptible hosts?

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Influenza viruses are unique because of their ability to alter antigenic (H and N) composition, thus reinfecting "nonimmume," susceptible hosts. Antigenic drift, caused by mutation during genome replication, results in minor antigenic change and relatively mild influenza outbreaks every 1 to 3 years. Antigenic shift, caused by reassortment or mixing of the segmented viral genome during co-infection in nonhuman animals, results in major antigenic change and periodic worldwide outbreaks (pandemics).

Which Viruses Are Unique Because of Their Ability to Alter