CDC confirmed the bird flu virus detected in a person in the US is an H5N1 virus. H5N1 bird flu viruses first emerged in mid-90s to cause poultry outbreaks and human infections with a greater than 60% mortality rate. Over time H5N1 viruses have evolved. Current H5N1 viruses spreading in wild birds and poultry in the US and globally are genetically different from earlier versions of the virus.
Learn more about the emergence and evolution of the H5N1 bird flu here.