Now that we know about both prokaryotic and eukaryotic cells, let's look at the endosymbiosis theory. This theory suggests that mitochondria and plastids in eukaryotic cells were once independent prokaryotic cells.
Avian influenza (AI) is an infectious viral disease of birds (especially wild water fowl such as ducks and geese), often causing no apparent signs of illness. AI viruses can sometimes spread to domestic poultry and cause large-scale outbreaks of serious disease.
A bird-adapted strain of H5N1, called HPAI A(H5N1) for highly pathogenic avian influenza virus of type A of subtype H5N1, is the highly pathogenic causative agent of H5N1 flu, commonly known as avian influenza (bird flu).