A pandemic is an outbreak of global proportions. It happens when a bacterium or novel virus becomes capable of spreading rapidly.It causes serious illness and can spread easily from one person to the next.The word pandemic comes from the Greek pandemos meaning "pertaining to all people." The Greek word pan means "all" and the Greek word demos means "people."This article discusses the difference between epidemics and pandemics, how pandemics start, and future concerns.Fast facts on pandemics