Lessons From Outbreaks of H1N1 Influenza

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   Figure. Reassortment of influenza virus.

   The influenza virus single-stranded RNA genome is organized into 8 segments. In a process known as reassortment, 2 or more viruses that co-infect the same cell can exchange 1 or more RNA segments to generate strains with new antigenic properties and new biological characteristics. During the 1957 “Asian influenza” pandemic, 3 genes from an avian H2N2 virus were introduced into a human H1N1 strain and created a new virus with pandemic capabilities. This exchange of genetic material probably occurred during the dual infection of a human or an animal, possibly a pig, with both viral strains. Derived from reference 25.