An epidemic is a disease that spreads rapidly among many people in a community at the same time. A pandemic is an outbreak of global proportions. It happens when a novel virus emerges among humans - it causes serious illness and is easily human transmissible (spreads easily from person-to-person). 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". A pandemic covers a much wider geographical area, often worldwide. A pandemic also infects many more people than an epidemic. An epidemic is specific to one city, region or country, while a pandemic goes much further than national borders. A pandemic is usually caused by a new virus strain or subtype - a virus humans either have no immunity against, or very little immunity. If immunity is low or non-existent the virus is much more likely to spread around the world if it becomes easily human transmissible. Pandemics generally cause much higher numbers of deaths than epidemics. The social disruption, economic loss, and general hardship caused by a pandemic are much higher than what an epidemic can cause. An epidemic is when the number of people who become infected rises well beyond what is expected within a country or a part of a country. When the infection takes place in several countries at the same time it then starts turning into a pandemic.