The correct answer is option 1: Endemic. An infection that is constantly maintained at a baseline level in a specific geographic area without any external input is considered endemic. This means that the infection is regularly present and maintained within the population of that area.

Option 2: Pandemic refers to a situation where an infectious disease spreads across multiple countries or continents, affecting a large number of people.

Option 3: Epidemic refers to the sudden increase in the number of cases of a disease within a specific community or population, exceeding the normal or expected levels.

Option 4: Outbreak refers to the occurrence of cases of a particular disease in a specific area or community that exceeds the normal expected number.

Therefore, the correct answer is option 1: Endemic, as it describes a situation where an infection maintains a constant baseline level in a geographic area without external input.