As mentioned yesterday, the term epidemic typically has been used to describe a condition in which contagious diseases spread rapidly among many people, in a section of a State of country or in the country as a whole.
Enters the word pandemic, from the Greek pandemos, meaning that it pertains to all people. Think of a pandemic as an epidemic that crosses international boundaries; contagious illnesses (often fatal) that affect large numbers of the population in multiple areas around the globe and perhaps on multiple continents. The World Health Organization (WHO) has a six-stage classification that describes the process by which a novel influenza virus moves from the first few infections in humans through to a pandemic. This starts with the virus mostly infecting animals, with a few cases where animals infect people, then moves through the stage where the virus begins to spread directly between people, and ends with a pandemic when infections from the new virus have spread worldwide and tends to be out of control until something can be done to stop it. More tomorrow.