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H5N1, the virus that causes avian influenza, is now circulating consistently in wild birds and waterfowl in North America, according to a study published late last year in the journal Nature.
Study: H5N1 primarily spread by wild birds and waterfowl
Outbreaks of avian influenza tend to hit backyard chicken flocks first, but this isn't the source of infection for most commercial flocks, virologist says.