Diseases that are either new to the human population or have historically existed in very low incidence are referred to as:

The term used to describe diseases that are either new to the human population or have historically existed at very low incidence is "emerging diseases." Emerging diseases can arise due to various factors, including changes in environmental conditions, human behavior, genetic mutations of pathogens, and increased global travel and trade, which can facilitate the spread of infectious agents to new areas or populations.

Emerging diseases are a significant concern in public health, as they may not only affect a large number of people but can also challenge existing medical and healthcare infrastructures. Understanding the dynamics of these diseases can help in developing effective prevention and control measures.

In contrast, chronic diseases refer to long-lasting conditions that can be controlled but not cured, typically with a gradual onset over time. Endemic diseases are those that are consistently present within a particular geographic area or population. Non-communicable diseases include conditions like cancers and heart disease that are not caused by infectious agents and are often linked to lifestyle choices rather than transmission dynamics.