Final answer:
Health defects that develop slowly and persist or often reoccur are known as chronic illnesses, lasting for extended periods unlike acute illnesses which are short-term.
Step-by-step explanation:
Adverse health defects that develop slowly over a long period of time and persist or reoccur frequently are called chronic illnesses. Unlike acute illnesses, which are short-term and often resolve quickly with or without treatment, chronic illnesses such as type 1 diabetes, cardiovascular diseases, and certain viral infections like herpes and HIV, can last for months, years, or even a lifetime. While acute diseases are characterized by a rapid onset and short duration, chronic diseases have an extended period of symptoms and may require ongoing medical care and management.