A pandemic (from Greek πᾶν pan "all" and δῆμος demos "people") is a disease epidemic that has spread across a large region, for instance multiple continents, or worldwide. A widespread endemic disease with a stable number of infected people is not a pandemic. Further, flu pandemics generally exclude recurrences of seasonal flu.
Throughout history, there have been a number of pandemics of diseases such as smallpox and tuberculosis. One of the most devastating pandemics was the Black Death (also known as The Plague), which killed an estimated 75–200 million people in the 14th century. Other notable pandemics include the 1918 influenza pandemic (Spanish flu) and the 2009 flu pandemic (H1N1). Current pandemics include HIV/AIDS and the 2019 coronavirus disease, which was declared a pandemic on 11 March 2020 by the World Health Organization (WHO).