The recent appearance of the H5N1 bird flu in pigs does raise viral reassortment concerns. Here's what we know about this highly pathogenic avian influenza virus so far.

H5 bird flu, a type of avian influenza, has infected dozens of people in the U.S., and spread to seven states and Canada this year.As concern grows over whether it could lead to another pandemic or lockdown,

With 55 human cases in the US and avian influenza impacting bird populations across the globe, here’s a look at why scientists are closely paying attention to any evolution of this virus. View on euro

In the 2009 swine flu pandemic, multiple reassortment events in pigs and birds led to the novel H1N1 virus strain, which led to 60 million cases and 12,000 deaths in the U.S. in its first year of circulating, per the CDC.