Step 1: Concept
Epidemiology uses specific terms to describe the frequency and distribution of diseases.
Step 2: Meaning
An unexpected surge in cases within a specific population or region is defined by its scale.
Step 3: Analysis
Endemic refers to a constant presence in an area; Pandemic refers to a global spread; Sporadic refers to occasional, irregular cases. An Epidemic is a sudden increase in cases above what is normally expected in that specific area.
Step 4: Conclusion
Therefore, the term for an unexpected regional increase in disease cases is an Epidemic.
Final Answer: (C)