Because rodents' teeth grow continuously, they must gnaw to keep them short. That may help to explain why chair legs or similar surfaces show gnawed spots or tooth marks in rodent-infested places. You Notice an Odd, Stale Smell. In closed-up rooms infested by rodents, you will commonly smell an unusual, musky odor. You See a Mouse in Your House.
Rodents are normally active at night, and generally avoid humans.
If you have rodents, unless the infestation is large, you may never see one. Remember that not all types of rodents carry hantavirus. Neither common house mice nor common rats have been associated with HPS in humans, for example. The image above may not print at actual size. However, you can download a .tif file of the same image.