A pandemic is an epidemic of an infectious disease that has spread across a large region, for instance multiple continents or worldwide, affecting a substantial number of individuals. Widespread endemic diseases with a stable number of infected individuals such as recurrences of seasonal influenza are generally excluded as they occur simultaneously in large regions of the globe rather than being spread worldwide.
Early in the COVID-19 pandemic, convention centers (pictured here) were deemed to be ideal sites for temporary hospitals, due to their existing infrastructure (electrical, water, sewage). Hotels and dormitories were also considered appropriate because they can use negative pressure technology.
Depiction of the burial of bodies during the Black Death, which killed up to half of Eurasia's population in the 14th century.
American Red Cross workers carry a body during the 1918–20 "Spanish flu" pandemic.
Social distancing in public
An epidemic is the rapid spread of disease to a large number of hosts in a given population within a short period of time. For example, in meningococcal infections, an attack rate in excess of 15 cases per 100,000 people for two consecutive weeks is considered an epidemic.
The Plague of Athens (c. 1652–1654) by Michiel Sweerts, illustrating the devastating epidemic that struck Athens in 430 BC, as described by the historian Thucydides
Anopheles mosquito, the vector of malaria
Possibilities for zoonotic disease transmissions