Usually, a disease is considered pandemic when it crosses international borders. A disease that does not cross international borders is an epidemic. An example of a pandemic would be the Black Plague (also called the Black Death or the Bubonic Plague), which killed most of the population of Western Medieval Europe.
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pandemic is the worldwide spread of a new disease. An influenza pandemic occurs when a new influenza virus emerges and spreads around the world, and most people do not have immunity. Viruses that have caused past pandemics typically originated from animal influenza viruses
