The antiscientific campaign to promote “living with the virus” The ancient Greek physician Hippocrates used the terms “endemic” and “epidemic” to distinguish between diseases that were always present in a population and diseases that only occurred during certain parts of a year or at yearly or even greater intervals. In epidemiological terms, endemic means the constant presence and prevalence of a disease within a population in a certain geographic area. It refers to a state when a disease reaches a level that most of the population has developed immunity. They can develop secondary infections though these are often mild. Children usually become the primary cases because they are naïve (not previously exposed) to the virus.