Definitions
Avian (bird) flu: caused by influenza viruses that occur naturally among wild birds. The H5N1 variant is deadly to domestic fowl and can be transmitted from birds to humans. There is no human immunity and no vaccine is available.
Influenza: a viral upper respiratory illness that comes on suddenly, causing a person to feel very sick with symptoms such as fever, body aches, headache, fatigue, loss of appetite, and a dry cough or sore, dry throat. Pandemic: widespread, general. In medicine, an epidemic over a wide geographic area and affecting a large proportion of the population.
Pandemic flu: virulent 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 no pandemic flu.
Quarantine: enforced isolation or restriction of free movement imposed to prevent the spread of contagious disease
Seasonal (common) flu: a respiratory illness that can be transmitted person to person. Most people have some immunity, and a vaccine is available.
Vaccine: a preparation of a weakened or killed pathogen, such as a bacterium or virus, or of a portion of the pathogen's structure that upon administration stimulates antibody production or cellular immunity against the pathogen but is incapable of causing severe infection. The single best way to prevent the flu is to get a flu vaccination each fall.