Diseases that are always present in a geographical area at a  constant frequency are called

Diseases that are consistently present in a specific geographical area at a constant frequency are known as endemic diseases. These diseases are expected to occur at a certain rate in the population as part of the normal health landscape of that area. Examples include malaria in certain tropical areas, the common cold in temperate regions, and chickenpox in various communities. The prevalence of endemic diseases can vary depending on environmental factors, public health measures, and population immunity. Endemicity is an important concept in epidemiology, aiding in understanding disease patterns, planning public health interventions, and anticipating health care needs.