The term reassortment refers to the establishment of a new viral strain and/or subtype (is a distinct variant of a virus, often used to characterize/classify viruses). This new viral strain occurs after two different viruses infect the same cell and form a ‘new’ virus. An example of this would be when an avian influenza and human influenza infect the same cell and form a new virus that no one has any immunity to allowing the new virus to spread very quickly. This has occurred many times in the past and will likely happen again.