According to the World Health Organization, an illness can be called a pandemic only under certain conditions. For example, it must be a new disease that emerges; it must cause serious illness in humans; and it must spread easily and quickly from person to person. Serious illnesses that affect large numbers of people but are not contagious (such as cancer) do not meet this description.
A pandemic is an infectious disease affecting the majority of the population of a large region. When people think of a pandemic, they may think of previous flu pandemics, such as the 1918 flu (also known as "Spanish flu") or the Hong Kong flu of 1968-1969. It can also be defined as an infectious disease that is an epidemic at the same time in many parts of the world.
What Makes Something a Pandemic?
According to the World Health Organization, a pandemic can start when three conditions have been met. The three conditions are:
- The emergence of a disease new to the population
- The agent infects humans, causing serious illness
- The agent spreads easily and sustainably among humans.
A disease or condition is not a pandemic specifically because it kills a large number of people. For example, cancer is responsible for a large number of deaths. But the deaths and disabilities due to cancer are not considered a pandemic because the condition is not infectious.
(Click Pandemic Flu for more information about a specific pandemic.)