The word pandemic (from the Greek language pan meaning ‘all’ and demos meaning ‘people’) is used to describe an epidemic that affects the whole population across every continent.
An influenza pandemic occurs when:
- a new subtype of influenza virus emerges in humans to which most people have not been previously exposed and are, therefore, highly susceptible
- the virus causes serious disease in humans
- the virus is easily and rapidly spread between humans, infecting large numbers of people worldwide and causing many deaths.