We got a complaint of mice in a rental home this month (April). I went to check it out and talked to the woman at the home. She told me that they moved in in mid December. They saw a few mice when they moved in and put some sticky traps down. She said the mice got much worse and they are now in every room in the house.
I inspected each room. The bedrooms on the second floor had an impressive amount of droppings in the closets. Oddly, the kitchen did not show much evidence of mice. The house was very clean and there was no obvious reason for the mice to be attracted to the 2nd floor bedroom areas. Something was going on. I decided to take a look in the basement and the women of the house said "you can't go down there because they are still working on the pipes". It was a mess. I went down there and looked around. There had been a big flood and obviously a lot of new pipes installed. The floor had standing water on it. I asked what happened down there. She told me that something broke after they moved in and there was a lot of water leaking. The owners fixed it.
My best guess is that the previous tenants had a lot of garbage in the basement. There was a build up of mice. Before the new tenants moved in, the garbage was cleaned out. The flooded floor drove the mice up into the residence in a mass movement. Lots of mice but not a lot of food sources. The tenants began seeing mice everywhere all at once. The woman told me that sometimes the mice wake her up by running down her arm while she is sleeping in bed. She also told me that her sister opened a kitchen drawer and a mouse ran up her arm.
I treated the place with a combination of traps, sticky boards, block bait, granular baits, and tracking powder. Each method was chosen to fit different situations in the home. I also blocked some obvious entry points on the outside. I followed up 4 days later. The woman said she had not seen any more mice.