The word epidemic comes from the Latin term “epi demos,” meaning “upon people.” Just having an infectious pathogen is not enough to cause an epidemic. In public health, we talk about three key parts of an “epidemiologic triangle” that must come together to cause an epidemic: 1) a pathogen (usually virus or bacteria); 2) a host (human or animal) that is susceptible to that pathogen; and 3) an environment that brings the pathogen and host together in a way that fosters spread. Understanding the epidemiological triangle is key to understanding why an outbreak occurs, and how to change parts of the triangle to stop the outbreak.
This is How Disease Outbreaks Like the Coronavirus Pandemic Occur – and how They can be Stopped
