Influenza, or flu, is a respiratory infection caused by a variety of flu viruses. The most familiar aspect of the flu is the way it can "knock you off your feet" as it sweeps through entire communities.
The flu differs in several ways from the common cold, a respiratory infection also caused by viruses. For example, people with colds rarely get fevers or headaches or suffer from the extreme exhaustion that flu viruses cause.
The Centers for Disease Control and Prevention (CDC) esti...

Bird flu is an infection caused by avian (bird) influenza (flu) viruses. These flu viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, bird flu is very contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them. Gold Bamboo Special Report on Bird Flu