Creating a Hybrid Virus
New strains of influenza A can emerge from genetic reassortment, which happens only when two or more viral strains infect the same host cell.
The lower half of the figure shows a second virus infecting the cell. (E) The two sets of RNA segments can mix in the nucleus (get reassorted), as represented by the exchange of two HA segments. The result is two hybrid viruses with their own traits and behaviors.
In this graph, each horizontal line corresponds to one of influenza’s eight RNA segments and groups of eight correspond to a viral subtype. Through reassortments, three subtypes evolved into six. The 2009 H1N1 swine flu virus resulted from a series of reassortments. It contains two RNA segments from H1N1 avian virus, one from H3N2 seasonal human virus, and five from pigs (H1N1 Classical swine virus and the Triple reassortant swine).
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