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.
Bird flu, or avian influenza, is a viral infection spread from bird to bird. Currently, a particularly deadly strain of bird flu -- H5N1 -- continues to spread among poultry in Egypt and in certain parts of Asia. Technically, H5N1 is a highly pathogenic avian influenza (HPAI) virus. It's deadly to most birds. And it's deadly to humans and to other mammals that catch the virus from birds.