A pandemic is a global disease outbreak or epidemic of infectious disease that spreads through populations across a large region. The world has seen several pandemics in the last 100 years, such as Cholera, Influenza (the Flu), Typhus, HIV/AIDS, SARS, and most recently, the H1N1 or Swine Flu. A flu pandemic occurs when a new influenza virus emerges for which people have little or no immunity, and for which there is no vaccine. The disease spreads easily person-to-person, causing serious illness, and can sweep across the country and around the world in very short time.
It is difficult to predict when the next influenza pandemic will occur or how severe it will be. Wherever and whenever a pandemic starts, everyone around the world is at risk. Countries might, through measures such as border closures and travel restrictions, delay arrival of the virus, but cannot stop it.For more information on the flu, see our Influenza (Flu) webpage.