Pandemic
When an epidemic involves a large number of people in a large number of countries, it is known as pandemic. There is a question as to whether or not the word can ever be properly used. It is claimed that the influenza epidemic of 1918-19 could really be considered pandemic in view of the fact that the condition was found in all countries.
These terms are used very loosely and are applied largely to suit the circumstances. A number of cases of a so-called contagious dis-ease occurring about the same time in a community may be considered an epidemic by some. There is no established rule designating the percentage of individuals that must be affected by the same condition in order that an epidemic may be established. An endemic dis-ease may become epidemic at certain times of the year or when a greater number of people than usual become affected. A sporadic dis-ease may become epidemic when a greater number of people become affected.