Swine flu: What is pandemic and epidemic?

In the last days the two words pandemic and epidemic appeared nearly in each newspaper and television program.

They talked about the illness that is caused by the swine flu which has its origin in the USA/Mexico. At the moment over 100 persons died already - not directly because of the virus from the swine but the virus can affect the human body.

The World Health Organization (WHO) is talking from an epidemic which could develop into a pandemic in the near future.

What is now exactly the difference between pandemic and epidemic?

Epidemic is a sickness which will affect thousands of persons within a specific area (country or even continent) and time frame (like at the moment many persons at the same time in Mexico and the USA).

Pandemic is when the epidemic is spreading from one country to several countries on different continents. In the past pandemics occur from persons who travelled worldwide by ship. In our time pandemics occur mainly by travelling with airplanes around the world.

Epidemic sicknesses are HIV, Bird/swine flu or SARS. The last flu epidemics have been in 1957 and 1968. They cost millions of persons their lives at that time.