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.
Avian influenza is an infectious disease of birds caused by type A strains of the influenza virus. To date, all outbreaks of the highly pathogenic form have been caused by influenza A viruses of subtypes H5 and H7.