What are the different types of influenza viruses?
The influenza viruses were first identified among birds. It caused extensive infection among birds resulting in their death in large numbers. But it was found that these viruses were not capable enough to cause similar symptoms in humans or other animals initially. Such type of viruses which were capable to affect only birds was called as avian influenza virus. In addition the avian influenza viruses over a period of time underwent changes in its structure and became potent enough to cause an infection in humans and pigs. Such modified influenza viruses were known as human influenza virus or swine influenza virus depending on the organism it affected.
