What describes diseases that have a gradual onset and long duration?

The term that describes diseases with a gradual onset and long duration is chronic. Chronic diseases are typically characterized by their slow progression, which may take weeks, months, or even years to develop fully. These conditions often persist over an extended period, resulting in ongoing and sometimes fluctuating symptoms that may not significantly impair the individual early on but can lead to serious health issues over time.

In contrast, acute diseases have a rapid onset and are typically short-lived. Peracute refers to a disease that appears suddenly and is very severe and intense, while local diseases are confined to a specific area of the body, rather than describing the duration or progression of the disease. Thus, chronic accurately captures the essence of illnesses that develop slowly and last for a long time.