Avian Flu

Avian influenza is caused by a virus that exists naturally in wild birds. Wild birds often do not become sick, but they carry the virus and can pass it on to non-wild birds, such as chickens, turkeys, and ducks (fowl), which can become very sick and die.

Bird flu viruses do not generally infect people, but there have been several instances of human infection from bird flu viruses since the first reported case in 1997. There are many different types, and only a few of them can make people sick, including the H5N1 strain recently seen in Asia, Africa and Europe.

Avian (or bird) flu is caused by influenza viruses that occur naturally among birds. The highly pathogenic H5N1 variant is deadly to domestic fowl (such as chickens) and can be transmitted from birds to people. The H7N9 strain does not appear to sicken birds, but it has been recently infecting people. 

• Seasonal (or regular) flu is a respiratory illness that can be transmitted person to person. Most people have some immunity, and a vaccine is available.
• Pandemic flu is a deadly human flu that causes a global outbreak, or pandemic, of serious illness. Because there is little natural immunity, the disease can spread easily from person to person. Currently, there is not pandemic flu in the world.

Influenza A is a family of viruses that affects birds and other animals. Avian influenza (also called "bird flu") refers to the strains of the virus that infect birds. Bird flu can cause widespread illness and death among birds, though there are many different strains, which vary in strength. All known subtypes of influenza circulate among wild birds, which are considered the natural host for influenza A viruses. Not all influenza A strains infect humans, however. Those that do can cause high death rates. There is much concern that a strain that infects people will change and easily transmit from person to person causing a global pandemic that kills millions.