endemic / epidemic / pandemic
Always present in a place, a sharp outbreak, and an outbreak over a wide area.
Endemic means regularly found in a place or a population. Epidemic means a sharp outbreak in a community. Pandemic means an outbreak over a wide area, often many countries. Do not use epidemic for a disease that is simply always there.
Examples
Useendemic in the valley
Usean epidemic in the county
Usea pandemic across three continents
Avoidan epidemic in the valley (If the illness is always there.)