We live in the 'burbs. Occasionally mice get in the attic. Keep glue traps up there just in case. The pest service will inspect for openings into the attic when they are spraying for ants. They close them off with caulking or steel wool shoved into any areas mice can squeeze through. Haven't had issues in the last 4 or 5 years. At one point they chewed through a pipe insulation to get in and it tool a week or two to get them all. The key is to address it quickly. If you wait, the house can get overrun fast.