Influenza viruses constantly change and produce new strains. A pandemic starts if a new influenza virus emerges.
In order to become a pandemic virus, an animal virus, usually an avian (bird) virus must mutate or mix with a human influenza virus and become able to spread from person to person. A pandemic influenza virus can spread quickly because it is new and most people have no immunity.
Diagram from: National Health Services, England.
Pandemic influenza is likely to be more severe than seasonal influenza. The groups or individuals at greatest risk will not be known until the pandemic spreads.
Pandemic influenza is expected to occur in waves, and may hit individual communities at different times. It could affect a community for a period of several weeks, then subside and reappear again several months later. There
could be up to three waves of pandemic influenza in
B.C. before the pandemic is finished.
A vaccine can be researched and made only after the new virus is identified. Antiviral treatment or drugs may be available during a pandemic, but they may be in limited supply, and their effectiveness against the pandemic strain is not yet known.
For tips on staying healthy, see Prevent Influenza. | 
