Which rodent left the droppings determines the risk, so identifying the species is part of protecting yourself.
House mice — the species behind nearly all indoor droppings — can shed Salmonella bacteria in their waste and are the natural carrier of lymphocytic choriomeningitis virus, or LCMV. Both spread through contaminated food, dust, and the surfaces mice simply walk across on their nightly rounds.
Hantavirus is a different story. In North America, it is tied to deer mice and a few other wild rodents, not to the common house mouse. That risk belongs to sheds, cabins, barns, and rural crawl spaces where deer mice nest.
Dry droppings are the practical hazard in every case. Sweeping or vacuuming crushes old pellets into fine dust that you then breathe, which is exactly the exposure route public health agencies warn about in enclosed, poorly ventilated spaces like attics and closed cabinets.
Droppings also trigger allergies and asthma. Mouse allergen is a documented indoor asthma trigger, and it concentrates in bedrooms, upholstered furniture, and children’s play areas where soft surfaces hold dust.
