For an that relies on person-to-person to be endemic, each person who becomes infected with the disease must pass it on to one other person on average. In this way, the infection neither dies out nor does the number of infected people increase.
About Endemic Infection and Disease Outbreaks
Sporadic refers to a disease that occurs infrequently and irregularly. Endemic refers to the constant presence and/or usual prevalence of a disease or infectious in a population within a geographic area. Hyperendemic refers to persistent, high levels of disease occurrence.
Occasionally, the amount of disease in a community rises above the expected level. refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area. Outbreak carries the same definition of epidemic, but is often used for a more limited geographic area.
Cluster refers to an aggregation of cases grouped in place and time that are suspected to be greater than the number expected, even though the expected number may not be known. refers to an that has spread over several countries or continents, usually affecting a large number of people.