Pandemic - What does that Mean?

An influenza pandemic is an epidemic of an influenza virus that spreads on a worldwide scale and infects a large proportion of the human population. In contrast to the regular seasonal epidemics of influenza, these pandemics occur irregularly, with the 1918 Spanish flu the most serious pandemic in recent history. Pandemics can cause high levels of mortality, with the Spanish influenza being responsible for the deaths of over 50 million people. There have been about 3 influenza pandemics in each century for the last 300 years. The most recent ones were the Asian Flu in 1957 and the Hong Kong Flu in 1968.